Core PHP Functions That Are Useful For WordPress Developers. Volume 1.

As a WordPress developer, it is very necessary to have a solid understanding of PHP, the programming language that serves as the platform’s backbone and is responsible for most of its functionality. While WordPress does come with its own set of specialised functions, having a working knowledge of the core PHP functions will dramatically improve your programming skills and enable you to build WordPress websites that are easier to manage, more secure, and more efficient. In this blog post, we are going to talk about some of the most important fundamental PHP functions that any WordPress developer ought to be familiar with.


The in_array() function is used to check if a value exists in an array. This function is particularly useful when working with arrays in WordPress, such as checking user capabilities or validating options. It returns a boolean value (true or false).

$array = array( 'apple', 'banana', 'orange' );

if ( in_array( 'banana', $array ) ) {
    echo 'Banana is in the array.';
} else {
    echo 'Banana is not in the array.';


The strpos() function searches for a specific substring within a larger string and returns the position of the first occurrence. This can be helpful for validating input or performing string manipulation tasks in WordPress.

$haystack = 'Hello, world!';
$needle = 'world';

if ( strpos( $haystack, $needle ) !== false ) {
    echo 'The word "world" was found in the string.';
} else {
    echo 'The word "world" was not found in the string.';

json_encode() and json_decode()

These two functions are essential for working with JSON data in WordPress, particularly when dealing with REST API requests or AJAX calls. json_encode() converts PHP arrays or objects into JSON strings, while json_decode() converts JSON strings back into PHP arrays or objects.

// Encode a PHP array into a JSON string
$array = array( 'name' => 'John', 'age' => 30 );
$json_string = json_encode( $array );

// Decode a JSON string into a PHP array
$json_string = '{"name":"John","age":30}';
$array = json_decode( $json_string, true );


The preg_match() function is a powerful tool for working with regular expressions in PHP. It can be used to validate input, extract data, or perform complex string manipulations in WordPress development tasks.

$email = '[email protected]';
$pattern = '/^[a-zA-Z0-9._%-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}$/';

if ( preg_match( $pattern, $email ) ) {
    echo 'The email address is valid.';
} else {
    echo 'The email address is not valid.';

file_get_contents() and file_put_contents()

These two functions are useful for reading and writing data to files. file_get_contents() reads the contents of a file into a string, while file_put_contents() writes a string to a file. These functions can be helpful when working with WordPress theme or plugin files, caching data, or managing custom configuration files.

// Read the contents of a file
$file_contents = file_get_contents( 'path/to/your/file.txt' );

// Write contents to a file
$new_contents = 'This is a new line.';
file_put_contents( 'path/to/your/file.txt', $new_contents );


You’ll become a more capable and versatile WordPress developer if you can master these essential PHP functions first. You will be able to better understand and troubleshoot the underlying code with the help of these functions, which serve as the basis for a large number of functions that are unique to WordPress. More to come in volume two!