What are the potential security risks of using a custom hash function in PHP, as opposed to established methods like bcrypt?

Using a custom hash function in PHP instead of established methods like bcrypt can pose security risks, as custom functions may not have undergone rigorous testing and may contain vulnerabilities that could be exploited by attackers. To mitigate these risks, it is recommended to use established and well-tested hashing algorithms like bcrypt, which are specifically designed for securely hashing passwords.

// Using bcrypt for secure password hashing
$hashed_password = password_hash($password, PASSWORD_BCRYPT);