sanitize_key() │ WP 3.0.0

Clears the string to use it as a key. Keys are used as different internal IDs.

Converts the string to lowercase (see strtolower()) and removes everything from the string except a-z0-9_-.

1 time — 0.000013 sec (very fast) | 50000 times — 0.04 sec (speed of light)
Hooks from the function

Returns

String. Cleaned key.

Usage

sanitize_key( $key );
$key(string) (required)
String that will be used as a key.

Examples

0

#1 Demo of cleaning

In code below is show how sanitize_key() clears string with uppercase & lowercase letters, numbers, dash, underscore, forward slash, brackets, spaces. 

echo sanitize_key( 'Testexample1-_/[]{}' ); // testexample1-_
echo sanitize_key( '  My Key  ' ); // mykey
echo sanitize_key( 'My-Key' ); // my-key
echo sanitize_key( 'My_Key' ); // my_key

So as you can see this function turn uppercase letter into lowercase, remove forward slash, spaces, brackets and any other non-standard characters.

Changelog

Since 3.0.0 Introduced.

sanitize_key() code WP 6.9.1

wp-includes/formatting.php 
function sanitize_key( $key ) {
	$sanitized_key = '';

	if ( is_scalar( $key ) ) {
		$sanitized_key = strtolower( $key );
		$sanitized_key = preg_replace( '/[^a-z0-9_\-]/', '', $sanitized_key );
	}

	/**
	 * Filters a sanitized key string.
	 *
	 * @since 3.0.0
	 *
	 * @param string $sanitized_key Sanitized key.
	 * @param string $key           The key prior to sanitization.
	 */
	return apply_filters( 'sanitize_key', $sanitized_key, $key );
}

sanitize_