json_last_error

(PHP 5 >= 5.3.0, PHP 7)

json_last_error — Returns the last error occurred

Description

int json_last_error ( void )

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

Parameters

This function has no parameters.

Return Values

Returns an integer, the value can be one of the following constants:

**JSON error codes**
Constant	Meaning	Availability
`JSON_ERROR_NONE`	No error has occurred
`JSON_ERROR_DEPTH`	The maximum stack depth has been exceeded
`JSON_ERROR_STATE_MISMATCH`	Invalid or malformed JSON
`JSON_ERROR_CTRL_CHAR`	Control character error, possibly incorrectly encoded
`JSON_ERROR_SYNTAX`	Syntax error
`JSON_ERROR_UTF8`	Malformed UTF-8 characters, possibly incorrectly encoded	PHP 5.3.3
`JSON_ERROR_RECURSION`	One or more recursive references in the value to be encoded	PHP 5.5.0
`JSON_ERROR_INF_OR_NAN`	One or more `NAN` or `INF` values in the value to be encoded	PHP 5.5.0
`JSON_ERROR_UNSUPPORTED_TYPE`	A value of a type that cannot be encoded was given	PHP 5.5.0

Examples

Example #1 json_last_error() example


<?php
// A valid json string
$json[] = '{"Organization": "PHP Documentation Team"}';

// An invalid json string which will cause an syntax 
// error, in this case we used ' instead of " for quotation
$json[] = "{'Organization': 'PHP Documentation Team'}";


foreach ($json as $string) {
    echo 'Decoding: ' . $string;
    json_decode($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;
    }

    echo PHP_EOL;
}
?>

The above example will output:

Decoding: {"Organization": "PHP Documentation Team"} - No errors
Decoding: {'Organization': 'PHP Documentation Team'} - Syntax error, malformed JSON

Example #2 json_last_error() with json_encode()


<?php
// An invalid UTF8 sequence
$text = "\xB1\x31";

$json  = json_encode($text);
$error = json_last_error();

var_dump($json, $error === JSON_ERROR_UTF8);
?>

The above example will output:

string(4) "null"
bool(true)

User Contributed Notes

jimmetry at gmail dot com

4 years ago


While this can obviously change between versions, the current error codes are as follows:

0 = JSON_ERROR_NONE
1 = JSON_ERROR_DEPTH
2 = JSON_ERROR_STATE_MISMATCH
3 = JSON_ERROR_CTRL_CHAR
4 = JSON_ERROR_SYNTAX
5 = JSON_ERROR_UTF8

I'm only posting these for people who may be trying to understand why specific JSON files are not being decoded. Please do not hard-code these numbers into an error handler routine.

praveenscience at gmail dot com

1 year ago


I used this simple script, flicked from StackOverflow to escape from the function failing:

<?php
    function utf8ize($d) {
        if (is_array($d)) {
            foreach ($d as $k => $v) {
                $d[$k] = utf8ize($v);
            }
        } else if (is_string ($d)) {
            return utf8_encode($d);
        }
        return $d;
    }
?>

Cheers,
Praveen Kumar!

hemono at gmail dot com

6 months ago


when json_decode a empty string, PHP7 will trigger an Syntax error:
<?php
json_decode("");
var_dump(json_last_error(), json_last_error_msg());

// PHP 7
int(4)
string(12) "Syntax error"

//  PHP 5
int(0)
string(8) "No error"

williamprogphp at yahoo dot com dot br

2 years ago


This is a quite simple and functional trick to validate JSON's strings.

<?php

    function json_validate($string) {
        if (is_string($string)) {
            @json_decode($string);
            return (json_last_error() === JSON_ERROR_NONE);
        }
        return false;
    }
    echo (json_validate('{"test": "valid JSON"}')  ? "It's a JSON" : "NOT is a JSON"); // prints 'It's a JSON'
    echo (json_validate('{test: valid JSON}')  ? "It's a JSON" : "NOT is a JSON"); // prints 'NOT is a JSON' due to missing quotes
    echo (json_validate(array())  ? "It's a JSON" : "NOT is a JSON"); // prints 'NOT is a JSON' due to a non-string argument
?>

Cheers

lior at mytopia dot com

7 years ago


For those of you who prefer a more object oriented approach (as I do), here is a fairly simple wrapper that handles errors using exceptions:

<?php

class JSON 
{
    public static function Encode($obj)
    {
        return json_encode($obj);
    }
    
    public static function Decode($json, $toAssoc = false)
    {
        $result = json_decode($json, $toAssoc);
        switch(json_last_error())
        {
            case JSON_ERROR_DEPTH:
                $error =  ' - Maximum stack depth exceeded';
                break;
            case JSON_ERROR_CTRL_CHAR:
                $error = ' - Unexpected control character found';
                break;
            case JSON_ERROR_SYNTAX:
                $error = ' - Syntax error, malformed JSON';
                break;
            case JSON_ERROR_NONE:
            default:
                $error = '';                    
        }
        if (!empty($error))
            throw new Exception('JSON Error: '.$error);        
        
        return $result;
    }
}

?>

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