<!DOCTYPE html><html><body><title>PHP Tutorial</title>

<h1>PHP Tutorial</h1>

<p>The PHP Hypertext Preprocessor (PHP) is a programming language that allows web developers to create dynamic content that interacts with databases. PHP is basically used for developing web based software applications. This tutorial helps you to build your base with PHP.</p>

<h1>Audience</h1>

<p>This tutorial is designed for PHP programmers who are completely unaware of PHP concepts but they have basic understanding on computer programming.</p>

<h1>Prerequisites</h1>

<p>Before proceeding with this tutorial you should have at least basic understanding of computer programming, Internet, Database, and MySQL etc is very helpful.</p>

<h1>PHP Offline Mobile App</h1>

<h1>Execute PHP Online</h1>

<p>For most of the examples given in this tutorial you will find <b>Try it</b> an option, so just make use of this option to execute your PHP programs at the spot and enjoy your learning.</p>

<p>Try following example using <b>Try it</b> option available at the top right corner of the below sample code box &minus;</p>

<p>&copy; Copyright 2017. All Rights Reserved.</p>

<pre class="prettyprint notranslate tryit">

&lt;html&gt;

&lt;head&gt;

&lt;title&gt;Online PHP Script Execution&lt;/title&gt;

&lt;/head&gt;

&lt;body&gt;

&lt;?php

echo "&lt;h1&gt;Hello, PHP!&lt;/h1&gt;";

?&gt;

&lt;/body&gt;

&lt;/html&gt;

<title>PHP Introduction</title>

<h1>PHP - Introduction</h1>

<p>PHP started out as a small open source project that evolved as more and more people found out how useful it was. Rasmus Lerdorf unleashed the first version of PHP way back in 1994.</p>

<p>PHP is a recursive acronym for "PHP: Hypertext Preprocessor".</p>

<p>PHP is a server side scripting language that is embedded in HTML. It is used to manage dynamic content, databases, session tracking, even build entire e-commerce sites.</p>

<p>It is integrated with a number of popular databases, including MySQL, PostgreSQL, Oracle, Sybase, Informix, and Microsoft SQL Server.</p>

<p>PHP is pleasingly zippy in its execution, especially when compiled as an Apache module on the Unix side. The MySQL server, once started, executes even very complex queries with huge result sets in record-setting time.</p>

<p>PHP supports a large number of major protocols such as POP3, IMAP, and LDAP. PHP4 added support for Java and distributed object architectures (COM and CORBA), making n-tier development a possibility for the first time.</p>

<p>PHP is forgiving: PHP language tries to be as forgiving as possible.</p>

<p>PHP Syntax is C-Like.</p>

<h2>Common uses of PHP</h2>

<p>PHP performs system functions, i.e. from files on a system it can create, open, read, write, and close them.</p>

<p>PHP can handle forms, i.e. gather data from files, save data to a file, through email you can send data, return data to the user.</p>

<p>You add, delete, modify elements within your database through PHP.</p>

<p>Access cookies variables and set cookies.</p>

<p>Using PHP, you can restrict users to access some pages of your website.</p>

<p>It can encrypt data.</p>

<h2>Characteristics of PHP</h2>

<p>Five important characteristics make PHP's practical nature possible &minus;</p>

<h2>"Hello World" Script in PHP</h2>

<p>To get a feel for PHP, first start with simple PHP scripts. Since "Hello, World!" is an essential example, first we will create a friendly little "Hello, World!" script.</p>

<p>As mentioned earlier, PHP is embedded in HTML. That means that in amongst your normal HTML (or XHTML if you're cutting-edge) you'll have PHP statements like this &minus;</p>

<p>It will produce following result &minus;</p>

<p>If you examine the HTML output of the above example, you'll notice that the PHP code is not present in the file sent from the server to your Web browser. All of the PHP present in the Web page is processed and stripped from the page; the only thing returned to the client from the Web server is pure HTML output.</p>

<p>All PHP code must be included inside one of the three special markup tags ate are recognised by the PHP Parser.</p>

<p>A most common tag is the &lt;?php...?&gt; and we will also use the same tag in our tutorial.</p>

<p>From the next chapter we will start with PHP Environment Setup on your machine and then we will dig out almost all concepts related to PHP to make you comfortable with the PHP language.</p>

<p>&copy; Copyright 2017. All Rights Reserved.</p>

<pre class="prettyprint notranslate tryit">

&lt;html&gt;

&lt;head&gt;

&lt;title&gt;Hello World&lt;/title&gt;

&lt;/head&gt;

&lt;body&gt;

&lt;?php echo "Hello, World!";?&gt;

&lt;/body&gt;

&lt;/html&gt;

<p>It will produce following result &minus;</p>

<pre class="result notranslate">

Hello, World!

<p>If you examine the HTML output of the above example, you'll notice that the PHP code is not present in the file sent from the server to your Web browser. All of the PHP present in the Web page is processed and stripped from the page; the only thing returned to the client from the Web server is pure HTML output.</p>

<p>All PHP code must be included inside one of the three special markup tags ate are recognised by the PHP Parser.</p>

<pre class="prettyprint notranslate">

&lt;?php PHP code goes here ?&gt;

&lt;? PHP code goes here ?&gt;

&lt;script language="php"&gt; PHP code goes here &lt;/script&gt;

<title>PHP Environment Setup Windows, Linux and Mac OS X</title>

<h1>PHP - Environment Setup</h1>

<h2>Try it Option Online</h2>

<p>We have set up the PHP Programming environment on-line, so that you can compile and execute all the available examples on line. It gives you confidence in what you are reading and enables you to verify the programs with different options. Feel free to modify any example and execute it on-line.</p>

<p>Try the following example using our on-line compiler available at <a href="http://www.tutorialspoint.com/codingground.htm" target="_blank" > CodingGround.</a></p>

<p>For most of the examples given in this tutorial, you will find a <b>Try it</b> option in our website code sections at the top right corner that will take you to the online compiler. So just make use of it and enjoy your learning.</p>

<p>In order to develop and run PHP Web pages three vital components need to be installed on your computer system.</p>

<p><b>Web Server</b> &minus; PHP will work with virtually all Web Server software, including Microsoft's Internet Information Server (IIS) but then most often used is freely available Apache Server. Download Apache for free here &minus; <a rel="nofollow" href="https://httpd.apache.org/download.cgi" target="_blank">https://httpd.apache.org/download.cgi</a></p>

<p><b>Database</b> &minus; PHP will work with virtually all database software, including Oracle and Sybase but most commonly used is freely available MySQL database. Download MySQL for free here &minus; <a rel="nofollow" target="_blank" href="https://www.mysql.com/downloads/">https://www.mysql.com/downloads/</a></p>

<p><b>PHP Parser</b> &minus; In order to process PHP script instructions a parser must be installed to generate HTML output that can be sent to the Web Browser. This tutorial will guide you how to install PHP parser on your computer.</p>

<h2>PHP Parser Installation</h2>

<p>Before you proceed it is important to make sure that you have proper environment setup on your machine to develop your web programs using PHP.</p>

<p>Type the following address into your browser's address box.</p>

<p>If this displays a page showing your PHP installation related information then it means you have PHP and Webserver installed properly. Otherwise you have to follow given procedure to install PHP on your computer.</p>

<p>This section will guide you to install and configure PHP over the following four platforms &minus;</p>

<p><a href="/php/php_installation_linux.htm">PHP Installation on Linux or Unix with Apache</a></p>

<p><a href="/php/php_installation_mac.htm">PHP Installation on Mac OS X with Apache</a></p>

<p><a href="/php/php_installation_windows_iis.htm">PHP Installation on Windows NT/2000/XP with IIS</a></p>

<p><a href="/php/php_installation_windows_apache.htm">PHP Installation on Windows NT/2000/XP with Apache</a></p>

<h3>Apache Configuration</h3>

<p>If you are using Apache as a Web Server then this section will guide you to edit Apache Configuration Files.</p>

<p>Just Check it here &minus; <a href="/php/php_apache_configuration.htm">PHP Configuration in Apache Server</a></p>

<h3>PHP.INI File Configuration</h3>

<p>The PHP configuration file, php.ini, is the final and most immediate way to affect PHP's functionality.</p>

<p>Just Check it here &minus; <a href="/php/php_ini_configuration.htm">PHP.INI File Configuration</a></p>

<h3>Windows IIS Configuration</h3>

<p>To configure IIS on your Windows machine you can refer your IIS Reference Manual shipped along with IIS.</p>

<p>&copy; Copyright 2017. All Rights Reserved.</p>

<pre class="prettyprint notranslate tryit">

&lt;html&gt;

&lt;head&gt;

&lt;title&gt;Online PHP Script Execution&lt;/title&gt;

&lt;/head&gt;

&lt;body&gt;

&lt;?php

echo "&lt;h1&gt;Hello, PHP!&lt;/h1&gt;";

?&gt;

&lt;/body&gt;

&lt;/html&gt;

<p>For most of the examples given in this tutorial, you will find a <b>Try it</b> option in our website code sections at the top right corner that will take you to the online compiler. So just make use of it and enjoy your learning.</p>

<p>In order to develop and run PHP Web pages three vital components need to be installed on your computer system.</p>

<ul class="list">

<li><p><b>Web Server</b> &minus; PHP will work with virtually all Web Server software, including Microsoft's Internet Information Server (IIS) but then most often used is freely available Apache Server. Download Apache for free here &minus; <a rel="nofollow" href="https://httpd.apache.org/download.cgi" target="_blank">https://httpd.apache.org/download.cgi</a></p></li>

<li><p><b>Database</b> &minus; PHP will work with virtually all database software, including Oracle and Sybase but most commonly used is freely available MySQL database. Download MySQL for free here &minus; <a rel="nofollow" target="_blank" href="https://www.mysql.com/downloads/">https://www.mysql.com/downloads/</a></p></li>

<li><p><b>PHP Parser</b> &minus; In order to process PHP script instructions a parser must be installed to generate HTML output that can be sent to the Web Browser. This tutorial will guide you how to install PHP parser on your computer.</p></li>

<h2>PHP Parser Installation</h2>

<p>Before you proceed it is important to make sure that you have proper environment setup on your machine to develop your web programs using PHP.</p>

<p>Type the following address into your browser's address box.</p>

<pre class="result notranslate">

http://127.0.0.1/info.php

<title>PHP Syntax Overview</title>

<h1>PHP - Syntax Overview</h1>

<p>This chapter will give you an idea of very basic syntax of PHP and very important to make your PHP foundation strong.</p>

<h2>Escaping to PHP</h2>

<p>The PHP parsing engine needs a way to differentiate PHP code from other elements in the page. The mechanism for doing so is known as 'escaping to PHP'. There are four ways to do this &minus;</p>

<h3>Canonical PHP tags</h3>

<p>The most universally effective PHP tag style is &minus;</p>

<p>If you use this style, you can be positive that your tags will always be correctly interpreted.</p>

<h3>Short-open (SGML-style) tags</h3>

<p>Short or short-open tags look like this &minus;</p>

<p>Short tags are, as one might expect, the shortest option You must do one of two things to enable PHP to recognize the tags &minus;</p>

<p>Choose the --enable-short-tags configuration option when you're building PHP.</p>

<p>Set the short_open_tag setting in your php.ini file to on. This option must be disabled to parse XML with PHP because the same syntax is used for XML tags.</p>

<h3>ASP-style tags</h3>

<p>ASP-style tags mimic the tags used by Active Server Pages to delineate code blocks. ASP-style tags look like this &minus;</p>

<p>To use ASP-style tags, you will need to set the configuration option in your php.ini file.</p>

<h3>HTML script tags</h3>

<p>HTML script tags look like this &minus;</p>

<h2>Commenting PHP Code</h2>

<p>A <i>comment</i> is the portion of a program that exists only for the human reader and stripped out before displaying the programs result. There are two commenting formats in PHP &minus;</p>

<p><b>Single-line comments</b> &minus; They are generally used for short explanations or notes relevant to the local code. Here are the examples of single line comments.</p>

<p><b>Multi-lines printing</b> &minus; Here are the examples to print multiple lines in a single print statement &minus;</p>

<p><b>Multi-lines comments</b> &minus; They are generally used to provide pseudocode algorithms and more detailed explanations when necessary. The multiline style of commenting is the same as in C. Here are the example of multi lines comments.</p>

<h2>PHP is whitespace insensitive</h2>

<p>Whitespace is the stuff you type that is typically invisible on the screen, including spaces, tabs, and carriage returns (end-of-line characters).</p>

<p>PHP whitespace insensitive means that it almost never matters how many whitespace characters you have in a row.one whitespace character is the same as many such characters.</p>

<p>For example, each of the following PHP statements that assigns the sum of 2 + 2 to the variable $four is equivalent &minus;</p>

<h2>PHP is case sensitive</h2>

<p>Yeah it is true that PHP is a case sensitive language. Try out following example &minus;</p>

<p>This will produce the following result &minus;</p>

<h2>Statements are expressions terminated by semicolons</h2>

<p>A <i>statement</i> in PHP is any expression that is followed by a semicolon (;).Any sequence of valid PHP statements that is enclosed by the PHP tags is a valid PHP program. Here is a typical statement in PHP, which in this case assigns a string of characters to a variable called $greeting &minus;</p>

<h2>Expressions are combinations of tokens</h2>

<p>The smallest building blocks of PHP are the indivisible tokens, such as numbers (3.14159), strings (.two.), variables ($two), constants (TRUE), and the special words that make up the syntax of PHP itself like if, else, while, for and so forth</p>

<h2>Braces make blocks</h2>

<p>Although statements cannot be combined like expressions, you can always put a sequence of statements anywhere a statement can go by enclosing them in a set of curly braces.</p>

<p>Here both statements are equivalent &minus;</p>

<h2>Running PHP Script from Command Prompt</h2>

<p>Yes you can run your PHP script on your command prompt. Assuming you have following content in test.php file</p>

<p>Now run this script as command prompt as follows &minus;</p>

<p>It will produce the following result &minus;</p>

<p>Hope now you have basic knowledge of PHP Syntax.</p>

<p>&copy; Copyright 2017. All Rights Reserved.</p>

<pre class="result notranslate">

&lt;?php...?&gt;

<p>If you use this style, you can be positive that your tags will always be correctly interpreted.</p>

<h3>Short-open (SGML-style) tags</h3>

<p>Short or short-open tags look like this &minus;</p>

<pre class="result notranslate">

&lt;?...?&gt;

<p>Short tags are, as one might expect, the shortest option You must do one of two things to enable PHP to recognize the tags &minus;</p>

<ul class="list">

<li><p>Choose the --enable-short-tags configuration option when you're building PHP.</p></li>

<li><p>Set the short_open_tag setting in your php.ini file to on. This option must be disabled to parse XML with PHP because the same syntax is used for XML tags.</p></li>

<h3>ASP-style tags</h3>

<p>ASP-style tags mimic the tags used by Active Server Pages to delineate code blocks. ASP-style tags look like this &minus;</p>

<pre class="result notranslate">

&lt;%...%&gt;

<p>To use ASP-style tags, you will need to set the configuration option in your php.ini file.</p>

<h3>HTML script tags</h3>

<p>HTML script tags look like this &minus;</p>

<pre class="prettyprint notranslate">

&lt;script language="PHP"&gt;...&lt;/script&gt;

<h2>Commenting PHP Code</h2>

<p>A <i>comment</i> is the portion of a program that exists only for the human reader and stripped out before displaying the programs result. There are two commenting formats in PHP &minus;</p>

<p><b>Single-line comments</b> &minus; They are generally used for short explanations or notes relevant to the local code. Here are the examples of single line comments.</p>

<pre class="prettyprint notranslate">

&lt;?

# This is a comment, and

# This is the second line of the comment

// This is a comment too. Each style comments only

print "An example with single line comments";

?&gt;

<p><b>Multi-lines printing</b> &minus; Here are the examples to print multiple lines in a single print statement &minus;</p>

<pre class="prettyprint notranslate">

&lt;?

# First Example

print &lt;&lt;&lt;END

This uses the "here document" syntax to output

multiple lines with $variable interpolation. Note

that the here document terminator must appear on a

line with just a semicolon no extra whitespace!

END;

# Second Example

print "This spans

multiple lines. The newlines will be

output as well";

?&gt;

<p><b>Multi-lines comments</b> &minus; They are generally used to provide pseudocode algorithms and more detailed explanations when necessary. The multiline style of commenting is the same as in C. Here are the example of multi lines comments.</p>

<pre class="prettyprint notranslate">

&lt;?

/* This is a comment with multiline

Author : Mohammad Mohtashim

Purpose: Multiline Comments Demo

Subject: PHP

*/

print "An example with multi line comments";

?&gt;

<h2>PHP is whitespace insensitive</h2>

<p>Whitespace is the stuff you type that is typically invisible on the screen, including spaces, tabs, and carriage returns (end-of-line characters).</p>

<p>PHP whitespace insensitive means that it almost never matters how many whitespace characters you have in a row.one whitespace character is the same as many such characters.</p>

<p>For example, each of the following PHP statements that assigns the sum of 2 + 2 to the variable $four is equivalent &minus;</p>

<pre class="prettyprint notranslate">

$four = 2 + 2; // single spaces

$four &lt;tab&gt;=&lt;tab2&lt;tab&gt;+&lt;tab&gt;2 ; // spaces and tabs

$four =

2+

2; // multiple lines

<h2>PHP is case sensitive</h2>

<p>Yeah it is true that PHP is a case sensitive language. Try out following example &minus;</p>

<pre class="prettyprint notranslate tryit">

&lt;html&gt;

&lt;body&gt;

&lt;?php

$capital = 67;

print("Variable capital is $capital&lt;br&gt;");

print("Variable CaPiTaL is $CaPiTaL&lt;br&gt;");

?&gt;

&lt;/body&gt;

&lt;/html&gt;

<p>This will produce the following result &minus;</p>

<pre class="result notranslate">

Variable capital is 67

Variable CaPiTaL is

<h2>Statements are expressions terminated by semicolons</h2>

<p>A <i>statement</i> in PHP is any expression that is followed by a semicolon (;).Any sequence of valid PHP statements that is enclosed by the PHP tags is a valid PHP program. Here is a typical statement in PHP, which in this case assigns a string of characters to a variable called $greeting &minus;</p>

<pre class="result notranslate">

$greeting = "Welcome to PHP!";

<h2>Expressions are combinations of tokens</h2>

<p>The smallest building blocks of PHP are the indivisible tokens, such as numbers (3.14159), strings (.two.), variables ($two), constants (TRUE), and the special words that make up the syntax of PHP itself like if, else, while, for and so forth</p>

<h2>Braces make blocks</h2>

<p>Although statements cannot be combined like expressions, you can always put a sequence of statements anywhere a statement can go by enclosing them in a set of curly braces.</p>

<p>Here both statements are equivalent &minus;</p>

<pre class="prettyprint notranslate">

if (3 == 2 + 1)

print("Good - I haven't totally lost my mind.&lt;br&gt;");

if (3 == 2 + 1) {

print("Good - I haven't totally");

print("lost my mind.&lt;br&gt;");

}

<h2>Running PHP Script from Command Prompt</h2>

<p>Yes you can run your PHP script on your command prompt. Assuming you have following content in test.php file</p>

<pre class="prettyprint notranslate tryit">

&lt;?php

echo "Hello PHP!!!!!";

?&gt;

<p>Now run this script as command prompt as follows &minus;</p>

<pre class="result notranslate">

$ php test.php

<p>It will produce the following result &minus;</p>

<pre class="result notranslate">

Hello PHP!!!!!

<title>PHP Variable Types</title>

<h1>PHP - Variable Types</h1>

<p>The main way to store information in the middle of a PHP program is by using a variable.</p>

<p>Here are the most important things to know about variables in PHP.</p>

<p>All variables in PHP are denoted with a leading dollar sign ($).</p>

<p>The value of a variable is the value of its most recent assignment.</p>

<p>Variables are assigned with the = operator, with the variable on the left-hand side and the expression to be evaluated on the right.</p>

<p>Variables can, but do not need, to be declared before assignment.</p>

<p>Variables in PHP do not have intrinsic types - a variable does not know in advance whether it will be used to store a number or a string of characters.</p>

<p>Variables used before they are assigned have default values.</p>

<p>PHP does a good job of automatically converting types from one to another when necessary.</p>

<p>PHP variables are Perl-like.</p>

<p>PHP has a total of eight data types which we use to construct our variables &minus;</p>

<p><b>Integers</b> &minus; are whole numbers, without a decimal point, like 4195.</p>

<p><b>Doubles</b> &minus; are floating-point numbers, like 3.14159 or 49.1.</p>

<p><b>Booleans</b> &minus; have only two possible values either true or false.</p>

<p><b>NULL</b> &minus; is a special type that only has one value: NULL.</p>

<p><b>Strings</b> &minus; are sequences of characters, like 'PHP supports string operations.'</p>

<p><b>Arrays</b> &minus; are named and indexed collections of other values.</p>

<p><b>Objects</b> &minus; are instances of programmer-defined classes, which can package up both other kinds of values and functions that are specific to the class.</p>

<p><b>Resources</b> &minus; are special variables that hold references to resources external to PHP (such as database connections).</p>

<p>The first five are <i>simple types</i>, and the next two (arrays and objects) are compound - the compound types can package up other arbitrary values of arbitrary type, whereas the simple types cannot.</p>

<p>We will explain only simple data type in this chapters. Array and Objects will be explained separately.</p>

<h2>Integers</h2>

<p>They are whole numbers, without a decimal point, like 4195. They are the simplest type .they correspond to simple whole numbers, both positive and negative. Integers can be assigned to variables, or they can be used in expressions, like so &minus;</p>

<p>Integer can be in decimal (base 10), octal (base 8), and hexadecimal (base 16) format. Decimal format is the default, octal integers are specified with a leading 0, and hexadecimals have a leading 0x.</p>

<p>For most common platforms, the largest integer is (2**31 . 1) (or 2,147,483,647), and the smallest (most negative) integer is . (2**31 . 1) (or .2,147,483,647).</p>

<h2>Doubles</h2>

<p>They like 3.14159 or 49.1. By default, doubles print with the minimum number of decimal places needed. For example, the code &minus;</p>

<p>It produces the following browser output &minus;</p>

<h2>Boolean</h2>

<p>They have only two possible values either true or false. PHP provides a couple of constants especially for use as Booleans: TRUE and FALSE, which can be used like so &minus;</p>

<h3>Interpreting other types as Booleans</h3>

<p>Here are the rules for determine the "truth" of any value not already of the Boolean type &minus;</p>

<p>If the value is a number, it is false if exactly equal to zero and true otherwise.</p>

<p>If the value is a string, it is false if the string is empty (has zero characters) or is the string "0", and is true otherwise.</p>

<p>Values of type NULL are always false.</p>

<p>If the value is an array, it is false if it contains no other values, and it is true otherwise. For an object, containing a value means having a member variable that has been assigned a value.</p>

<p>Valid resources are true (although some functions that return resources when they are successful will return FALSE when unsuccessful).</p>

<p>Don't use double as Booleans.</p>

<p>Each of the following variables has the truth value embedded in its name when it is used in a Boolean context.</p>

<h2>NULL</h2>

<p>NULL is a special type that only has one value: NULL. To give a variable the NULL value, simply assign it like this &minus;</p>

<p>The special constant NULL is capitalized by convention, but actually it is case insensitive; you could just as well have typed &minus;</p>

<p>A variable that has been assigned NULL has the following properties &minus;</p>

<p>It evaluates to FALSE in a Boolean context.</p>

<p>It returns FALSE when tested with IsSet() function.</p>

<h2>Strings</h2>

<p>They are sequences of characters, like "PHP supports string operations". Following are valid examples of string</p>

<p>Singly quoted strings are treated almost literally, whereas doubly quoted strings replace variables with their values as well as specially interpreting certain character sequences.</p>

<p>This will produce following result &minus;</p>

<p>There are no artificial limits on string length - within the bounds of available memory, you ought to be able to make arbitrarily long strings.</p>

<p>Strings that are delimited by double quotes (as in "this") are preprocessed in both the following two ways by PHP &minus;</p>

<p>Certain character sequences beginning with backslash (\) are replaced with special characters</p>

<p>Variable names (starting with $) are replaced with string representations of their values.</p>

<p>The escape-sequence replacements are &minus;</p>

<h3>Here Document</h3>

<p>You can assign multiple lines to a single string variable using here document &minus;</p>

<p>This will produce following result &minus;</p>

<h2>Variable Scope</h2>

<p>Scope can be defined as the range of availability a variable has to the program in which it is declared. PHP variables can be one of four scope types &minus;</p>

<p><a href="/php/php_local_variables.htm">Local variables</a></p>

<p><a href="/php/php_function_parameters.htm">Function parameters</a></p>

<p><a href="/php/php_global_variables.htm">Global variables</a></p>

<p><a href="/php/php_static_variables.htm">Static variables</a></p>

<h2>Variable Naming</h2>

<p>Rules for naming a variable is &minus;</p>

<p>Variable names must begin with a letter or underscore character.</p>

<p>A variable name can consist of numbers, letters, underscores but you cannot use characters like + , - , % , ( , ) . &amp; , etc</p>

<p>There is no size limit for variables.</p>

<p>&copy; Copyright 2017. All Rights Reserved.</p>

<pre class="prettyprint notranslate">

$int_var = 12345;

$another_int = -12345 + 12345;

<p>Integer can be in decimal (base 10), octal (base 8), and hexadecimal (base 16) format. Decimal format is the default, octal integers are specified with a leading 0, and hexadecimals have a leading 0x.</p>

<p>For most common platforms, the largest integer is (2**31 . 1) (or 2,147,483,647), and the smallest (most negative) integer is . (2**31 . 1) (or .2,147,483,647).</p>

<h2>Doubles</h2>

<p>They like 3.14159 or 49.1. By default, doubles print with the minimum number of decimal places needed. For example, the code &minus;</p>

<pre class="prettyprint notranslate tryit">

&lt;?php

$many = 2.2888800;

$many_2 = 2.2111200;

$few = $many + $many_2;

print("$many + $many_2 = $few &lt;br&gt;");

?&gt;

<p>It produces the following browser output &minus;</p>

<pre class="result notranslate">

2.28888 + 2.21112 = 4.5

<h2>Boolean</h2>

<p>They have only two possible values either true or false. PHP provides a couple of constants especially for use as Booleans: TRUE and FALSE, which can be used like so &minus;</p>

<pre class="prettyprint notranslate">

if (TRUE)

print("This will always print&lt;br&gt;");

else

print("This will never print&lt;br&gt;");

<h3>Interpreting other types as Booleans</h3>

<p>Here are the rules for determine the "truth" of any value not already of the Boolean type &minus;</p>

<ul class="list">

<li><p>If the value is a number, it is false if exactly equal to zero and true otherwise.</p></li>

<li><p>If the value is a string, it is false if the string is empty (has zero characters) or is the string "0", and is true otherwise.</p></li>

<li><p>Values of type NULL are always false.</p></li>

<li><p>If the value is an array, it is false if it contains no other values, and it is true otherwise. For an object, containing a value means having a member variable that has been assigned a value.</p></li>

<li><p>Valid resources are true (although some functions that return resources when they are successful will return FALSE when unsuccessful).</p></li>

<li><p>Don't use double as Booleans.</p></li>

<p>Each of the following variables has the truth value embedded in its name when it is used in a Boolean context.</p>

<pre class="prettyprint notranslate">

$true_num = 3 + 0.14159;

$true_str = "Tried and true"

$true_array[49] = "An array element";

$false_array = array();

$false_null = NULL;

$false_num = 999 - 999;

$false_str = "";

<h2>NULL</h2>

<p>NULL is a special type that only has one value: NULL. To give a variable the NULL value, simply assign it like this &minus;</p>

<pre class="prettyprint notranslate">

$my_var = NULL;

<p>The special constant NULL is capitalized by convention, but actually it is case insensitive; you could just as well have typed &minus;</p>

<pre class="prettyprint notranslate">

$my_var = null;

<p>A variable that has been assigned NULL has the following properties &minus;</p>

<ul class="list">

<li><p>It evaluates to FALSE in a Boolean context.</p></li>

<li><p>It returns FALSE when tested with IsSet() function.</p></li>

<h2>Strings</h2>

<p>They are sequences of characters, like "PHP supports string operations". Following are valid examples of string</p>

<pre class="prettyprint notranslate">

$string_1 = "This is a string in double quotes";

$string_2 = 'This is a somewhat longer, singly quoted string';

$string_39 = "This string has thirty-nine characters";

$string_0 = ""; // a string with zero characters

<p>Singly quoted strings are treated almost literally, whereas doubly quoted strings replace variables with their values as well as specially interpreting certain character sequences.</p>

<pre class="prettyprint notranslate tryit">

&lt;?php

$variable = "name";

$literally = 'My $variable will not print!';

print($literally);

print "&lt;br&gt;";

$literally = "My $variable will print!";

print($literally);

?&gt;

<p>This will produce following result &minus;</p>

<pre class="result notranslate">

My $variable will not print!\n

My name will print

<p>There are no artificial limits on string length - within the bounds of available memory, you ought to be able to make arbitrarily long strings.</p>

<p>Strings that are delimited by double quotes (as in "this") are preprocessed in both the following two ways by PHP &minus;</p>

<ul class="list">

<li><p>Certain character sequences beginning with backslash (\) are replaced with special characters</p></li>

<li><p>Variable names (starting with $) are replaced with string representations of their values.</p></li>

<p>The escape-sequence replacements are &minus;</p>

<ul class="list">

<li>\n is replaced by the newline character</li>

<li>\r is replaced by the carriage-return character</li>

<li>\t is replaced by the tab character</li>

<li>\$ is replaced by the dollar sign itself ($)</li>

<li>\" is replaced by a single double-quote (")</li>

<li>\\ is replaced by a single backslash (\)</li>

<h3>Here Document</h3>

<p>You can assign multiple lines to a single string variable using here document &minus;</p>

<pre class="prettyprint notranslate tryit">

&lt;?php

$channel =&lt;&lt;&lt;_XML_

&lt;channel&gt;

&lt;title&gt;What's For Dinner&lt;/title&gt;

&lt;link&gt;http://menu.example.com/ &lt;/link&gt;

&lt;description&gt;Choose what to eat tonight.&lt;/description&gt;

&lt;/channel&gt;

_XML_;

echo &lt;&lt;&lt;END

This uses the "here document" syntax to output multiple lines with variable

interpolation. Note that the here document terminator must appear on a line with

just a semicolon. no extra whitespace!

<br />

END;

print $channel;

?&gt;

<p>This will produce following result &minus;</p>

<pre class="result notranslate">

This uses the "here document" syntax to output

multiple lines with variable interpolation. Note

that the here document terminator must appear on a

line with just a semicolon. no extra whitespace!

&lt;channel&gt;

&lt;title&gt;What's For Dinner&lt;title&gt;

&lt;link&gt;http://menu.example.com/&lt;link&gt;

&lt;description&gt;Choose what to eat tonight.&lt;/description&gt;

<title>PHP Constants Types</title>

<h1>PHP - Constants Types</h1>

<p>A constant is a name or an identifier for a simple value. A constant value cannot change during the execution of the script. By default, a constant is case-sensitive. By convention, constant identifiers are always uppercase. A constant name starts with a letter or underscore, followed by any number of letters, numbers, or underscores. If you have defined a constant, it can never be changed or undefined.</p>

<p>To define a constant you have to use define() function and to retrieve the value of a constant, you have to simply specifying its name. Unlike with variables, you do not need to have a constant with a $. You can also use the function constant() to read a constant's value if you wish to obtain the constant's name dynamically.</p>

<h2>constant() function</h2>

<p>As indicated by the name, this function will return the value of the constant.</p>

<p>This is useful when you want to retrieve value of a constant, but you do not know its name, i.e. It is stored in a variable or returned by a function.</p>

<h2>constant() example</h2>

<p>Only scalar data (boolean, integer, float and string) can be contained in constants.</p>

<h2>Differences between constants and variables are</h2>

<p>There is no need to write a dollar sign ($) before a constant, where as in Variable one has to write a dollar sign.</p>

<p>Constants cannot be defined by simple assignment, they may only be defined using the define() function.</p>

<p>Constants may be defined and accessed anywhere without regard to variable scoping rules.</p>

<p>Once the Constants have been set, may not be redefined or undefined.</p>

<h2>Valid and invalid constant names</h2>

<h2>PHP Magic constants</h2>

<p>PHP provides a large number of predefined constants to any script which it runs.</p>

<p>There are five magical constants that change depending on where they are used. For example, the value of __LINE__ depends on the line that it's used on in your script. These special constants are case-insensitive and are as follows &minus;</p>

<p>A few "magical" PHP constants are given below &minus;</p>

<p><b>__LINE__</b></p>

<p>The current line number of the file.</p>

<p><b>__FILE__</b></p>

<p>The full path and filename of the file. If used inside an include,the name of the included file is returned. Since PHP 4.0.2, <b>__FILE__</b> always contains an absolute path whereas in older versions it contained relative path under some circumstances.</p>

<p><b>__FUNCTION__</b></p>

<p>The function name. (Added in PHP 4.3.0) As of PHP 5 this constant returns the function name as it was declared (case-sensitive). In PHP 4 its value is always lowercased.</p>

<p><b>__CLASS__</b></p>

<p>The class name. (Added in PHP 4.3.0) As of PHP 5 this constant returns the class name as it was declared (case-sensitive). In PHP 4 its value is always lowercased.</p>

<p><b>__METHOD__</b></p>

<p>The class method name. (Added in PHP 5.0.0) The method name is returned as it was declared (case-sensitive).</p>

<p>&copy; Copyright 2017. All Rights Reserved.</p>

<pre class="prettyprint notranslate">

&lt;?php

define("MINSIZE", 50);

echo MINSIZE;

echo constant("MINSIZE"); // same thing as the previous line

?&gt;

<p>Only scalar data (boolean, integer, float and string) can be contained in constants.</p>

<h2>Differences between constants and variables are</h2>

<ul class="list">

<li><p>There is no need to write a dollar sign ($) before a constant, where as in Variable one has to write a dollar sign.</p></li>

<li><p>Constants cannot be defined by simple assignment, they may only be defined using the define() function.</p></li>

<li><p>Constants may be defined and accessed anywhere without regard to variable scoping rules.</p></li>

<li><p>Once the Constants have been set, may not be redefined or undefined.</p></li>

<h2>Valid and invalid constant names</h2>

<pre class="result notranslate">

// Valid constant names

define("ONE", "first thing");

define("TWO2", "second thing");

define("THREE_3", "third thing");

// Invalid constant names

define("2TWO", "second thing");

define("__THREE__", "third value");

<title>PHP Operator Types</title>

<h1>PHP - Operator Types</h1>

<p><b>What is Operator?</b> Simple answer can be given using expression <i>4 + 5 is equal to 9</i>. Here 4 and 5 are called operands and + is called operator. PHP language supports following type of operators.</p>

<p>Lets have a look on all operators one by one.</p>

<h2>Arithmetic Operators</h2>

<p>There are following arithmetic operators supported by PHP language &minus;</p>

<p>Assume variable A holds 10 and variable B holds 20 then &minus;</p>

<p><a href="/php/php_arithmatic_operators_examples.htm">Show Examples</a></p>

<h2>Comparison Operators</h2>

<p>There are following comparison operators supported by PHP language</p>

<p>Assume variable A holds 10 and variable B holds 20 then &minus;</p>

<p><a href="/php/php_comparison_operators_examples.htm">Show Examples</a></p>

<h2>Logical Operators</h2>

<p>There are following logical operators supported by PHP language</p>

<p>Assume variable A holds 10 and variable B holds 20 then &minus;</p>

<p><a href="/php/php_logical_operators_examples.htm">Show Examples</a></p>

<h2>Assignment Operators</h2>

<p>There are following assignment operators supported by PHP language &minus;</p>

<p><a href="/php/php_assignment_operators_examples.htm">Show Examples</a></p>

<h2>Conditional Operator</h2>

<p>There is one more operator called conditional operator. This first evaluates an expression for a true or false value and then execute one of the two given statements depending upon the result of the evaluation. The conditional operator has this syntax &minus;</p>

<p><a href="/php/php_conditional_operator_examples.htm">Show Examples</a></p>

<h2>Operators Categories</h2>

<p>All the operators we have discussed above can be categorised into following categories &minus;</p>

<p>Unary prefix operators, which precede a single operand.</p>

<p>Binary operators, which take two operands and perform a variety of arithmetic and logical operations.</p>

<p>The conditional operator (a ternary operator), which takes three operands and evaluates either the second or third expression, depending on the evaluation of the first expression.</p>

<p>Assignment operators, which assign a value to a variable.</p>

<h2>Precedence of PHP Operators</h2>

<p>Operator precedence determines the grouping of terms in an expression. This affects how an expression is evaluated. Certain operators have higher precedence than others; for example, the multiplication operator has higher precedence than the addition operator &minus;</p>

<p>For example x = 7 + 3 * 2; Here x is assigned 13, not 20 because operator * has higher precedence than + so it first get multiplied with 3*2 and then adds into 7.</p>

<p>Here operators with the highest precedence appear at the top of the table, those with the lowest appear at the bottom. Within an expression, higher precedence operators will be evaluated first.</p>

<p>&copy; Copyright 2017. All Rights Reserved.</p>

<title>PHP Decision Making IF ELSE and Switch Statements</title>

<h1>PHP - Decision Making</h1>

<p>The if, elseif ...else and switch statements are used to take decision based on the different condition.</p>

<p>You can use conditional statements in your code to make your decisions. PHP supports following three decision making statements &minus;</p>

<p><b>if...else statement</b> &minus; use this statement if you want to execute a set of code when a condition is true and another if the condition is not true</p>

<p><b>elseif statement</b> &minus; is used with the if...else statement to execute a set of code if <b>one</b> of the several condition is true</p>

<p><b>switch statement</b> &minus; is used if you want to select one of many blocks of code to be executed, use the Switch statement. The switch statement is used to avoid long blocks of if..elseif..else code.</p>

<h2>The If...Else Statement</h2>

<p>If you want to execute some code if a condition is true and another code if a condition is false, use the if....else statement.</p>

<h3>Syntax</h3>

<h3>Example</h3>

<p>The following example will output &quot;Have a nice weekend!&quot; if the current day is Friday, Otherwise, it will output &quot;Have a nice day!&quot;:</p>

<p>It will produce the following result &minus;</p>

<h2>The ElseIf Statement</h2>

<p>If you want to execute some code if one of the several conditions are true use the elseif statement</p>

<h3>Syntax</h3>

<h3>Example</h3>

<p>The following example will output &quot;Have a nice weekend!&quot; if the current day is Friday, and &quot;Have a nice Sunday!&quot; if the current day is Sunday. Otherwise, it will output &quot;Have a nice day!&quot; &minus;</p>

<p>It will produce the following result &minus;</p>

<h2>The Switch Statement</h2>

<p>If you want to select one of many blocks of code to be executed, use the Switch statement.</p>

<p>The switch statement is used to avoid long blocks of if..elseif..else code.</p>

<h3>Syntax</h3>

<h3>Example</h3>

<p>The <i>switch</i> statement works in an unusual way. First it evaluates given expression then seeks a lable to match the resulting value. If a matching value is found then the code associated with the matching label will be executed or if none of the lable matches then statement will execute any specified default code.</p>

<p>It will produce the following result &minus;</p>

<p>&copy; Copyright 2017. All Rights Reserved.</p>

<pre class="result notranslate">

if (<i>condition</i>)

<i>code to be executed if condition is true;</i>

else

<i>code to be executed if condition is false;</i>

<h3>Example</h3>

<p>The following example will output &quot;Have a nice weekend!&quot; if the current day is Friday, Otherwise, it will output &quot;Have a nice day!&quot;:</p>

<pre class="prettyprint notranslate tryit">

&lt;html&gt;

&lt;body&gt;

&lt;?php

$d = date(&quot;D&quot;);

if ($d == &quot;Fri&quot;)

echo &quot;Have a nice weekend!&quot;;

else

echo &quot;Have a nice day!&quot;;

?&gt;

&lt;/body&gt;

&lt;/html&gt;

<p>It will produce the following result &minus;</p>

<pre class="result notranslate">

Have a nice day!

<h2>The ElseIf Statement</h2>

<p>If you want to execute some code if one of the several conditions are true use the elseif statement</p>

<h3>Syntax</h3>

<pre class="result notranslate">

if (<i>condition</i>)

<i>code to be executed if condition is true;</i>

elseif (<i>condition</i>)

<i>code to be executed if condition is true;</i>

else

<i>code to be executed if condition is false;</i>

<h3>Example</h3>

<p>The following example will output &quot;Have a nice weekend!&quot; if the current day is Friday, and &quot;Have a nice Sunday!&quot; if the current day is Sunday. Otherwise, it will output &quot;Have a nice day!&quot; &minus;</p>

<pre class="prettyprint notranslate tryit">

&lt;html&gt;

&lt;body&gt;

&lt;?php

$d = date(&quot;D&quot;);

if ($d == &quot;Fri&quot;)

echo &quot;Have a nice weekend!&quot;;

elseif ($d == &quot;Sun&quot;)

echo &quot;Have a nice Sunday!&quot;;

else

echo &quot;Have a nice day!&quot;;

?&gt;

&lt;/body&gt;

&lt;/html&gt;

<p>It will produce the following result &minus;</p>

<pre class="result notranslate">

Have a nice day!

<h2>The Switch Statement</h2>

<p>If you want to select one of many blocks of code to be executed, use the Switch statement.</p>

<p>The switch statement is used to avoid long blocks of if..elseif..else code.</p>

<h3>Syntax</h3>

<pre class="result notranslate">

switch (<i>expression</i>){

case <i>label1:</i>

<i>code to be executed if expression = label1;</i>

break;

case <i>label2:</i>

<i>code to be executed if expression = label2;</i>

break;

default:

<i>code to be executed