Guzzle's method for "validating" JSON

json_decode.php

<?php

/**
 * Wrapper for JSON decode that implements error detection with helpful error
 * messages.
 *
 * @param string $json    JSON data to parse
 * @param bool   $assoc   When true, returned objects will be converted into
 *                        associative arrays.
 * @param int    $depth   User specified recursion depth.
 * @param int    $options Bitmask of JSON decode options.
 *
 * @return mixed
 * @throws \InvalidArgumentException if the JSON cannot be parsed.
 * @link http://www.php.net/manual/en/function.json-decode.php
 */
function json_decode($json, $assoc = false, $depth = 512, $options = 0)
{
    static $jsonErrors = [
        JSON_ERROR_DEPTH => 'JSON_ERROR_DEPTH - Maximum stack depth exceeded',
        JSON_ERROR_STATE_MISMATCH => 'JSON_ERROR_STATE_MISMATCH - Underflow or the modes mismatch',
        JSON_ERROR_CTRL_CHAR => 'JSON_ERROR_CTRL_CHAR - Unexpected control character found',
        JSON_ERROR_SYNTAX => 'JSON_ERROR_SYNTAX - Syntax error, malformed JSON',
        JSON_ERROR_UTF8 => 'JSON_ERROR_UTF8 - Malformed UTF-8 characters, possibly incorrectly encoded'
    ];
    $data = \json_decode($json, $assoc, $depth, $options);
    if (JSON_ERROR_NONE !== json_last_error()) {
        $last = json_last_error();
        throw new \InvalidArgumentException(
            'Unable to parse JSON data: '
            . (isset($jsonErrors[$last]) ? $jsonErrors[$last] : 'Unknown error')
        );
    }
    return $data;
}