php check valid json string

1function isJson($string) {
2 json_decode($string);
3 return (json_last_error() == JSON_ERROR_NONE);
4}

1//Simple
2if (is_object(json_decode($var))) { 
3  ....
4}
5
6//Else
7var $x = json_decode($var);
8var $y = is_object($x)?$x:....;
9
10//Better
11function json_validate($string) {
12    // decode the JSON data
13    $result = json_decode($string);
14
15    // switch and check possible JSON errors
16    switch (json_last_error()) {
17        case JSON_ERROR_NONE:
18            $error = ''; // JSON is valid // No error has occurred
19            break;
20        case JSON_ERROR_DEPTH:
21            $error = 'The maximum stack depth has been exceeded.';
22            break;
23        case JSON_ERROR_STATE_MISMATCH:
24            $error = 'Invalid or malformed JSON.';
25            break;
26        case JSON_ERROR_CTRL_CHAR:
27            $error = 'Control character error, possibly incorrectly encoded.';
28            break;
29        case JSON_ERROR_SYNTAX:
30            $error = 'Syntax error, malformed JSON.';
31            break;
32        // PHP >= 5.3.3
33        case JSON_ERROR_UTF8:
34            $error = 'Malformed UTF-8 characters, possibly incorrectly encoded.';
35            break;
36        // PHP >= 5.5.0
37        case JSON_ERROR_RECURSION:
38            $error = 'One or more recursive references in the value to be encoded.';
39            break;
40        // PHP >= 5.5.0
41        case JSON_ERROR_INF_OR_NAN:
42            $error = 'One or more NAN or INF values in the value to be encoded.';
43            break;
44        case JSON_ERROR_UNSUPPORTED_TYPE:
45            $error = 'A value of a type that cannot be encoded was given.';
46            break;
47        default:
48            $error = 'Unknown JSON error occured.';
49            break;
50    }
51
52    if ($error !== '') {
53        // throw the Exception or exit // or whatever :)
54        exit($error);
55    }
56    // everything is OK
57    return $result;
58}
59$output = json_validate($json);

1@json_decode($page_str);
2$json_OK=	json_last_error() == JSON_ERROR_NONE;
3