PHP Unconference Europe 2015

json_last_error

(PHP 5 >= 5.3.0)

json_last_errorReturns 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

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)

See Also

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User Contributed Notes 4 notes

up
72
jimmetry at gmail dot com
2 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.
up
7
williamprogphp at yahoo dot com dot br
9 months 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
up
1
praveenscience at gmail dot com
9 days 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!
up
-21
lior at mytopia dot com
5 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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