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function is not described

hash_equals() WP 3.9.2

Timing attack safe string comparison

Compares two strings using the same time whether they're equal or not.

Note: It can leak the length of a string when arguments of differing length are supplied.

This function was added in PHP 5.6. However, the Hash extension may be explicitly disabled on select servers. As of PHP 7.4.0, the Hash extension is a core PHP extension and can no longer be disabled. I.e. when PHP 7.4.0 becomes the minimum requirement, this polyfill can be safely removed.

No Hooks.

Return

true/false. Whether strings are equal.

Usage

hash_equals( $a, $b );
$a(string) (required)
Expected string.
$b(string) (required)
Actual, user supplied, string.

Changelog

Since 3.9.2 Introduced.

Code of hash_equals() WP 5.5.1

<?php
function hash_equals( $a, $b ) {
	$a_length = strlen( $a );
	if ( strlen( $b ) !== $a_length ) {
		return false;
	}
	$result = 0;

	// Do not attempt to "optimize" this.
	for ( $i = 0; $i < $a_length; $i++ ) {
		$result |= ord( $a[ $i ] ) ^ ord( $b[ $i ] );
	}

	return 0 === $result;
}