Understanding PHP Keywords

Keywords are predefined, reserved words used in programming languages that cannot be used as identifiers for variables, functions, classes, or other elements in a program. In this article, we will discuss the PHP keywords and their usage.

What are PHP Keywords?

PHP keywords are predefined, reserved words in PHP that are used to perform specific functions. These keywords are reserved by PHP and cannot be used as variable names, function names, or class names. PHP keywords are case-insensitive, meaning that they can be written in either upper or lower case letters.

List of PHP Keywords

Here is a list of PHP keywords:

abstract   and       array     as        break     callable
case       catch     class     clone     const     continue
declare    default   die       do        echo      else
elseif     empty     enddeclare endfor   endforeach endif
endswitch  endwhile  extends   final     finally   for
foreach    function  global    goto      if        implements
include    include_once   instanceof  insteadof  interface
isset      list      namespace new       or        print
private    protected public    require   require_once return
static     switch    throw     trait     try       unset
use        var       while     xor       yield     __halt_compiler

Usage of PHP Keywords

Keywords are used in PHP to define certain statements, constructs, and functions. For example, the if keyword is used to define a conditional statement, the while keyword is used to define a loop, and the function keyword is used to define a function.

Here is an example of using some of the PHP keywords:


$x = 7;
// Define a conditional statement
if ($x == 5) {
    echo "x is equal to 5.";

// Define a loop
for ($i = 0; $i < 10; $i++) {
    echo $i;

// Define a function
function add($a, $b)
    return $a + $b;

In this example, we use the if keyword to define a conditional statement that checks whether the value of $x is equal to 5. We use the for keyword to define a loop that iterates from 0 to 9. Finally, we use the function keyword to define a function that takes two parameters and returns their sum.


Keywords are an important part of any programming language, including PHP. By understanding the meaning and usage of PHP keywords, you can write more effective and efficient code. In addition, using keywords correctly can help prevent errors and make your code more readable and maintainable.

Practice Your Knowledge

Which of the following are reserved keywords in PHP?

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