Detect bad json data in PHP json_decode()?

问题:

I'm trying handle bad json data when parsed through json_decode(). I'm using the following script:

if(!json_decode($_POST)) {   echo "bad json data!";   exit; } 

If $_POST equals:

'{ bar: "baz" }' 

Then json_decode handles the error fine and spits out "bad json data!"; However, if I set $_POST to something like "invalid data", it gives me:

Warning: json_decode() expects parameter 1 to be string, array given in C:\server\www\myserver.dev\public_html\rivrUI\public_home\index.php  on line 6 bad json data! 

Do I need to write a custom script to detect valid json data, or is there some other nifty way to detect this?

回答1:

Here are a couple of things about json_decode :

• it returns the data, or null when there is an error
• it can also return null when there is no error : when the JSON string contains null
• it raises a warning where there is a warning -- warning that you want to make disappear.

To solve the warning problem, a solution would be to use the @ operator (I don't often recommend using it, as it makes debuging a lot more harder... But here, there is not much of a choice) :

$_POST = array(     'bad data' ); $data = @json_decode($_POST); 

You'd then have to test if $data is null -- and, to avoid the case in which json_decode returns null for null in the JSON string, you could check json_last_error, which (quoting) :

Returns the last error (if any) occurred by last JSON parsing.

Which means you'd have to use some code like the following :

if ($data === null     && json_last_error() !== JSON_ERROR_NONE) {     echo "incorrect data"; } 

回答2:

You can also use json_last_error : http://php.net/manual/en/function.json-last-error.php

which as documentation says :

Returns the last error (if any) occurred during the last JSON encoding/decoding.

here is an example

json_decode($string);  switch (json_last_error()) {     case JSON_ERROR_NONE:         echo ' - No errors';     break;     case JSON_ERROR_DEPTH:         echo ' - Maximum stack depth exceeded';     break;     case JSON_ERROR_STATE_MISMATCH:         echo ' - Underflow or the modes mismatch';     break;     case JSON_ERROR_CTRL_CHAR:         echo ' - Unexpected control character found';     break;     case JSON_ERROR_SYNTAX:         echo ' - Syntax error, malformed JSON';     break;     case JSON_ERROR_UTF8:         echo ' - Malformed UTF-8 characters, possibly incorrectly encoded';     break;     default:         echo ' - Unknown error';     break; } 

回答3:

This is how Guzzle handles json

    /**  * Parse the JSON response body and return an array  *  * @return array|string|int|bool|float  * @throws RuntimeException if the response body is not in JSON format  */ public function json() {     $data = json_decode((string) $this->body, true);     if (JSON_ERROR_NONE !== json_last_error()) {         throw new RuntimeException('Unable to parse response body into JSON: ' . json_last_error());     }      return $data === null ? array() : $data; } 

回答4:

I just broke my head over a json syntax error in what appeared to be perfect json: {"test1":"car", "test2":"auto"} from a url encoded string.

But in my case some of the above was html encoded, as adding html_entity_decode($string) did the trick.

$ft = json_decode(html_entity_decode(urldecode(filter_input(INPUT_GET, 'ft', FILTER_SANITIZE_STRING)))); 

Hopefully this will save someone else some time.

回答5:

/** * * custom json_decode * handle json_decode errors * * @param type $json_text * @return type */ public static function custom_json_decode($json_text) {

    $decoded_array = json_decode($json_text, TRUE);     switch (json_last_error()) {         case JSON_ERROR_NONE:             return array(                 "status" => 0,                 "value" => $decoded_array             );           case JSON_ERROR_DEPTH:             return array(                 "status" => 1,                 "value" => 'Maximum stack depth exceeded'             );          case JSON_ERROR_STATE_MISMATCH:             return array(                 "status" => 1,                 "value" => 'Underflow or the modes mismatch'             );          case JSON_ERROR_CTRL_CHAR:             return array(                 "status" => 1,                 "value" => 'Unexpected control character found'             );          case JSON_ERROR_SYNTAX:             return array(                 "status" => 1,                 "value" => 'Syntax error, malformed JSON'             );          case JSON_ERROR_UTF8:             return array(                 "status" => 1,                 "value" => 'Malformed UTF-8 characters, possibly incorrectly encoded'             );          default:             return array(                 "status" => 1,                 "value" => 'Unknown error'             );     } } 

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