function CryptoJSAesEncrypt($passphrase, $plain_text){

    $salt = openssl_random_pseudo_bytes(256);
    $iv = openssl_random_pseudo_bytes(16);
    //on PHP7 can use random_bytes() istead openssl_random_pseudo_bytes()
    //or PHP5x see : https://github.com/paragonie/random_compat

    $iterations = 999;  
    $key = hash_pbkdf2("sha512", $passphrase, $salt, $iterations, 64);

    $encrypted_data = openssl_encrypt($plain_text, 'aes-256-cbc', hex2bin($key), OPENSSL_RAW_DATA, $iv);

    $data = array("ciphertext" => base64_encode($encrypted_data), "iv" => bin2hex($iv), "salt" => bin2hex($salt));
    return json_encode($data);
}

$string_json_fromPHP = CryptoJSAesEncrypt("your passphrase", "your plain text");