We can easily encrypt and decrypt the password in php using the code below. First need to create key and string and pass it on to the encrypt function which are given below for encryption.

$key = 'password for encrypt or decrypt';
$string = ' string which requires for encryption ';

For encrytion $var = mcrypt_create_iv( mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC), MCRYPT_DEV_URANDOM );

$encrypted = base64_encode(
    $var .
    mcrypt_encrypt(
        MCRYPT_RIJNDAEL_128,
        hash('sha256', $key, true),
        $string,
        MCRYPT_MODE_CBC,
        $var
    )
);

for Decryption

$data = base64_decode($encrypted);
$var = substr($data, 0, mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC));

$decrypted = rtrim(
    mcrypt_decrypt(
        MCRYPT_RIJNDAEL_128,
        hash('sha256', $key, true),
        substr($data, mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC)),
        MCRYPT_MODE_CBC,
        $var
    ),
    "\0"
);