Encrypt/decrypt object to be stored secure from prying eyes

objencrypt.php

<?php

/**
 * Encrypts object to be stored secure from prying eyes (uses AES-256 ECB).
 *
 * @param object $sourceObj Object to be encrypted.
 * @param string $key       Key to use for encryption.
 * @return string           Encrypted object.
 */
function objEncrypt($sourceObj, $key)
{
    $sourceJson = json_encode($sourceObj, JSON_FORCE_OBJECT);

    $ciphertext = base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, sha1($key,true), $sourceJson, MCRYPT_MODE_ECB));

    return $ciphertext;
}

/**
 * Decrypts encrypted object.
 *
 * @param $cipherObj  Encrypted object.
 * @param string $key Key used for encryption.
 * @return object     Original object.
 */
function objDecrypt($cipherObj, $key)
{
    $sourceJson = mcrypt_decrypt(MCRYPT_RIJNDAEL_256, sha1($key,true), base64_decode($cipherObj), MCRYPT_MODE_ECB);

    $obj = json_decode(rtrim($sourceJson, "\0"));

    return $obj;
}