PHP Syntax

Summary: in this tutorial, you’ll learn basic PHP syntax, including case sensitivity, statements, and whitespaces.

As a programming language, PHP has a set of rules that governs how you write programs.

PHP code

Like HTML, you need to have the opening tag to start PHP code:

<?phpCode language: HTML, XML (xml)

If you mix PHP code with HTML, you need to have the enclosing tag:

?>Code language: PHP (php)

For example:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>PHP Syntax</title>
</head>
<body>
        <h1><?php echo 'PHP Syntax'; ?></h1>
</body>
</html>Code language: HTML, XML (xml)

However, if a file contains only PHP code, the enclosing tag is optional:

<?php
	echo 'PHP Syntax';Code language: HTML, XML (xml)

Case sensitivity

PHP is partially case-sensitive. Knowing what are case sensitive and what is not is very important to avoid syntax errors.

If you have a function such as count, you can use it as COUNT. It would work properly.

The following are case-insensitive in PHP:

PHP constructs such as if, if-else, if-elseif, switch, while, do-while, etc.
Keywords such as true and false.
User-defined function & class names.

On the other hand, variables are case-sensitive. e.g., $message and $MESSAGE are different variables.

Statements

A PHP script typically consists of one or more statements. A statement is a code that does something, e.g., assigning a value to a variable and calling a function.

A statement always ends with a semicolon (;). The following shows a statement that assigns a literal string to the $message variable:

$message = "Hello";Code language: PHP (php)

The above example is a simple statement. PHP also has a compound statement that consists of one or more simple statements. A compound statement uses curly braces to mark a block of code. For example:

if( $is_new_user ) {
    send_welcome_email();
}Code language: PHP (php)

You don’t need to place the semicolon after the curly brace (}).

The closing tag of a PHP block (?>) automatically implies a semicolon (;). Therefore, you don’t need to place a semicolon in the last statement in a PHP block. For example:

<?php echo $name ?>Code language: HTML, XML (xml)

In this example, the statement echo $name doesn’t need a semicolon. However, using a semicolon for the last statement in a block should work fine. For example:

<?php echo $name; ?>Code language: HTML, XML (xml)

Note that it’s OK if the code may not make any sense to you now because you’ll learn more about them in the upcoming tutorial.

Whitespace & line breaks

In most cases, whitespace and line breaks don’t have special meaning in PHP. Therefore, you can place a statement in one line or span it across multiple lines.

For example, the following code snippets are equivalent:

login( $username, $password );Code language: PHP (php)

And:

login( 
   $username,
   $password
);Code language: PHP (php)

Summary

PHP is partially case-sensitive.
PHP constructs, function names, class names are case-insensitive, whereas variables are case-sensitive.
A statement ends with a semicolon (;).
Whitespace and line breaks don’t matter in PHP; do leverage them to make the code more readable.

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