What are common errors when trying to create a login function in PHP, and how can they be resolved?

One common error when creating a login function in PHP is not properly hashing the password before comparing it with the stored hashed password in the database. To resolve this, you should use a secure hashing algorithm like password_hash() when storing the password and password_verify() when checking it during login.

// Store hashed password in the database
$hashed_password = password_hash($password, PASSWORD_DEFAULT);

// Verify hashed password during login
if(password_verify($password, $hashed_password)) {
    // Password is correct
} else {
    // Password is incorrect
}