json_last_error

(PHP 5 >= 5.3.0, PHP 7)

Returns the last error occurred

int json_last_error ( void )

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

Returns:

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:

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

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)