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PHP 5 Syntax

PHP 5 Syntax

PHP 5 Syntax

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Basic PHP Syntax

A PHP script can be placed anywhere in the document.

A PHP script starts with :
// 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:
Example

<!DOCTYPE html>
<html>
<body>

<h1>My first PHP page</h1>

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

</body>
</html>


Note: PHP statements are terminated by semicolon (;). The closing tag of a block of PHP code also automatically implies a semicolon (so you do not have to have a semicolon terminating the last line of a PHP block).
Comments in PHP

A comment in PHP code is a line that is not read/executed as part of the program. Its only purpose is to be read by someone who is editing the code!

Comments are useful for:

    To let others understand what you are doing - Comments let other programmers understand what you were doing in each step (if you work in a group)
    To remind yourself what you did - Most programmers have experienced coming back to their own work a year or two later and having to re-figure out what they did. Comments can remind you of what you were thinking when you wrote the code

PHP supports three ways of commenting:
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 more than
one line
*/
?>

</body>
</html>


PHP Case Sensitivity

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

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

<!DOCTYPE html>
<html>
<body>

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

</body>
</html>


However; in PHP, all variables are case-sensitive.

In the example below, only the first statement will display the value of the $color variable (this is because $color, $COLOR, and $coLOR are treated as three different variables):
Example

<!DOCTYPE html>
<html>
<body>

<?php
$color="red";
echo "My car is " . $color . "<br>";
echo "My house is " . $COLOR . "<br>";
echo "My boat is " . $coLOR . "<br>";
?>

</body>
</html>








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