PHP implements simple symmetric encryption and decryption methods

/**
 * Universal encryption
 * @param String $string The string that needs to be encrypted
 * @param String $skey Encrypted EKY
 * @return String
*/
function enCode($string = '', $skey = 'echounion') {
    $skey = array_reverse(str_split($skey));
    $strArr = str_split(base64_encode($string));
    $strCount = count($strArr);
    foreach ($skey as $key => $value) {
        $key < $strCount && $strArr[$key].=$value;
    }
    return str_replace('=', 'O0O0O', join('', $strArr));
}

/**
 * Universal decryption
 * @param String $string The string to be decrypted
 * @param String $skey Decryption KEY
 * @return String
*/
function deCode($string = '', $skey = 'echounion') {
    $skey = array_reverse(str_split($skey));
    $strArr = str_split(str_replace('O0O0O', '=', $string), 2);
    $strCount = count($strArr);
    foreach ($skey as $key => $value) {
        $key < $strCount && $strArr[$key] = rtrim($strArr[$key], $value);
    }
    return base64_decode(join('', $strArr));
}

PHP