How to Validate Password Strength in PHP

Using Regex (Regular Expression), you can easily validate the password strength in PHP. In the example code, we will show you how to check password strength and validate a strong password in PHP using Regex.

The following code snippet, validate the password using preg_match() function in PHP with Regular Expression, to check whether it is strong and difficult to guess.

• Password must be at least 8 characters in length.
• Password must include at least one upper case letter.
• Password must include at least one number.
• Password must include at least one special character.

// Given password
$password = 'your password string';

// Validate password strength
$uppercase = preg_match('@[A-Z]@', $password);
$lowercase = preg_match('@[a-z]@', $password);
$number    = preg_match('@[0-9]@', $password);
$specialChars = preg_match('@[^\w]@', $password);

if(!$uppercase || !$lowercase || !$number || !$specialChars || strlen($password) < 8) {
    echo 'Password should be at least 8 characters in length and should include at least one upper case letter, one number, and one special character.';
}else{
    echo 'Strong password.';
}

• answered 5 years ago
• Community  wiki

Following you will find a function that checks a string if it matches certain limitations that are usually applied on passwords.

Specifically, in the following code we check that the input contains at least one small letter, a caps letter, a number and a special character.

//Function that checks if string has at least 8 characters in length and one small letter, one caps letter, a number and a special character
 
function validPass($string) {
        $containsSmallLetter = preg_match('/[a-z]/', $string);
        $containsCapsLetter = preg_match('/[A-Z]/', $string);
        $containsDigit = preg_match('/\d/', $string);
        $containsSpecial = preg_match('/[^a-zA-Z\d]/', $string);

        return ($containsSmallLetter && $containsCapsLetter && $containsDigit && $containsSpecial && strlen($string) < 8);
    }

• answered 5 years ago
• Community  wiki

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• answered 5 years ago
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