Learn PHP for Developing Web Application

Learn to build web applications with PHP and MySQL, Start your own blog, e-commerce site. In this tutorial you will learn basic, syntax, examples, functions, loops, cookies, sessions, file handling, data connectivity, etc.

PHP TUTORIAL

PHP Syntax

A PHP script is executed on the server, and the plain HTML result is sent back to the browser.

Basic PHP Syntax

A PHP script can be placed anywhere in the document.

A PHP script starts with <?php and ends with ?>:

<?php
// PHP code goes here
?>

The default file extension for PHP files is ".php".

A PHP file normally contains HTML tags, and some PHP scripting code.

Below, we have an example of a simple PHP file, with a PHP script that uses a built-in PHP function "echo" to output the text "Hello World!" on a web page:

See this example:

<!DOCTYPE html>
<html>
<body>

<h1>My first PHP page</h1>

<?php
echo "Hello World!";
?>

</body>
</html>

Comments in PHP

A comment is the portion of a program that exists only for the human reader and stripped out before displaying the programs result.

See this example:

<!DOCTYPE html>
<html>
<body>

<?php
// This is a single-line comment

# This is also a single-line comment

/*
This is a multiple-lines comment block
that spans over multiple
lines
*/

// You can also use comments to leave out parts of a code line
$x = 5 /* + 15 */ + 5;
echo $x;
?>

</body>
</html>

PHP Case Sensitivity

In PHP, all keywords (e.g. if, else, while, echo, etc.), classes, functions, and user-defined functions are NOT case-sensitive.

In the example below, all three echo statements below are legal (and equal):

See this example:

<!DOCTYPE html>
<html>
<body>

<?php
ECHO "Hello World!<br>";
echo "Hello World!<br>";
EcHo "Hello World!<br>";
?>

</body>
</html>

However; all variable names are case-sensitive.

In the example below, only the first statement will display the value of the $book variable (this is because $book, $BOOK, and $BoOk are treated as three different variables):

See this example:

<!DOCTYPE html>
<html>
<body>

<?php
$book = "red";
echo "This is my " . $book . "<br>";
echo "Ths is Java" . $BOOK . "<br>";
echo "This is PHP " . $BoOk . "<br>";
?>

</body>
</html>
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