Function to create a save hash for passwords (very hard to brute force)

hash.fnc.php

<?php

define('PASSWORD_ALGO', 'sha512'); // hash will have 128 chars
define('PASSWORD_SALT', 'change_me_pls'); // a static string
define('PASSWORD_CYCLES', 12345); // number between 10.000 and 20.000
define('PASSWORD_DIVERSITY', 3); // number greater than 2

/**
 * Generates a save password hash
 * 
 * @param string $password    The raw password
 * @param string $salt        A salt specifically for this user/login
 * @return string             A hash
 */
function save_hash_password(string $password, string $salt = ''): string {
    for ($i = 0; $i < PASSWORD_CYCLES; $i++) {
        if ($i % PASSWORD_DIVERSITY == 0) {
            $password = hash(PASSWORD_ALGO, $salt . $i . PASSWORD_SALT . $password);
        } else {
            $password = hash(PASSWORD_ALGO, $password . PASSWORD_SALT . $i . $salt);
        }
    }
    
    return $password;
}

Hash.php

<?php

/**
 * The same logic as the function but as a class
 */
class Hash {
    private const PASSWORD_ALGO      = 'sha512'; // hash will have 128 chars
    private const PASSWORD_SALT      = 'change_me_pls'; // a static string
    private const PASSWORD_CYCLES    = 12345; // number between 10.000 and 20.000
    private const PASSWORD_DIVERSITY = 3; // number greater than 2

    /**
     * Generates a save password hash
     * 
     * @param string $password    The raw password
     * @param string $salt        A salt specifically for this user/login
     * @return string             A hash
     */
    public function createHash(string $password, string $salt = ''): string {
        for ($i = 0; $i < self::PASSWORD_CYCLES; $i++) {
            if ($i % self::PASSWORD_DIVERSITY == 0) {
                $password = hash(self::PASSWORD_ALGO, $salt . $i . self::PASSWORD_SALT . $password);
            } else {
                $password = hash(self::PASSWORD_ALGO, $password . self::PASSWORD_SALT . $i . $salt);
            }
        }
        
        return $password;
    }
}