How do you Encrypt and Decrypt a PHP String?

Question

What I mean is:

Original String + Salt or Key --> Encrypted String
Encrypted String + Salt or Key --> Decrypted (Original String)

May

Answer 1

What not to do

WARNING:
This answer uses ECB. ECB is not an encryption mode, it's only a building block. Using ECB as demonstrated in this answer does not actually encrypt the string securely. Do not use ECB in your code. See Scott's answer for a good solution.

I got it on myself. Actually i found some answer on google and just modified something. The result is completely insecure however.

";
echo $decrypted = decrypt($encrypted, ENCRYPTION_KEY);

/**
 * Returns an encrypted & utf8-encoded
 */
function encrypt($pure_string, $encryption_key) {
    $iv_size = mcrypt_get_iv_size(MCRYPT_BLOWFISH, MCRYPT_MODE_ECB);
    $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
    $encrypted_string = mcrypt_encrypt(MCRYPT_BLOWFISH, $encryption_key, utf8_encode($pure_string), MCRYPT_MODE_ECB, $iv);
    return $encrypted_string;
}

/**
 * Returns decrypted original string
 */
function decrypt($encrypted_string, $encryption_key) {
    $iv_size = mcrypt_get_iv_size(MCRYPT_BLOWFISH, MCRYPT_MODE_ECB);
    $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
    $decrypted_string = mcrypt_decrypt(MCRYPT_BLOWFISH, $encryption_key, $encrypted_string, MCRYPT_MODE_ECB, $iv);
    return $decrypted_string;
}
?>