json_last_error

While this can obviously change between versions, the current error codes are as follows:0 = JSON_ERROR_NONE1 = JSON_ERROR_DEPTH2 = JSON_ERROR_STATE_MISMATCH3 = JSON_ERROR_CTRL_CHAR4 = JSON_ERROR_SYNTAX5 = JSON_ERROR_UTF8I'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.

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!

when json_decode a empty string, PHP7 will trigger an Syntax error:<?phpjson_decode("");var_dump(json_last_error(), json_last_error_msg());// PHP 7int(4)string(12) "Syntax error"//  PHP 5int(0)string(8) "No error"

use this code with mb_convert_encoding, you can json_encode some corrupt UTF-8 chars    function safe_json_encode($value, $options = 0, $depth = 512) {        $encoded = json_encode($value, $options, $depth);        if ($encoded === false && $value && json_last_error() == JSON_ERROR_UTF8) {            $encoded = json_encode(utf8ize($value), $options, $depth);        }        return $encoded;    }    function utf8ize($mixed) {        if (is_array($mixed)) {            foreach ($mixed as $key => $value) {                $mixed[$key] = utf8ize($value);            }        } elseif (is_string($mixed)) {            return mb_convert_encoding($mixed, "UTF-8", "UTF-8");        }        return $mixed;    }

Just adding this note since I had to code this for the actual values reference.<?phpecho JSON_ERROR_NONE . ' JSON_ERROR_NONE' . '<br />';echo JSON_ERROR_DEPTH . ' JSON_ERROR_DEPTH' . '<br />';echo JSON_ERROR_STATE_MISMATCH . ' JSON_ERROR_STATE_MISMATCH' . '<br />';echo JSON_ERROR_CTRL_CHAR . ' JSON_ERROR_CTRL_CHAR' . '<br />';echo JSON_ERROR_SYNTAX . ' JSON_ERROR_SYNTAX' . '<br />';echo JSON_ERROR_UTF8 . ' JSON_ERROR_UTF8' . '<br />';echo JSON_ERROR_RECURSION . ' JSON_ERROR_RECURSION' . '<br />';echo JSON_ERROR_INF_OR_NAN . ' JSON_ERROR_INF_OR_NAN' . '<br />';echo JSON_ERROR_UNSUPPORTED_TYPE . ' JSON_ERROR_UNSUPPORTED_TYPE' . '<br />';/*The above outputs :0 JSON_ERROR_NONE1 JSON_ERROR_DEPTH2 JSON_ERROR_STATE_MISMATCH3 JSON_ERROR_CTRL_CHAR4 JSON_ERROR_SYNTAX5 JSON_ERROR_UTF86 JSON_ERROR_RECURSION7 JSON_ERROR_INF_OR_NAN8 JSON_ERROR_UNSUPPORTED_TYPE*/?>

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

Protected and private properties are ignored,when json_encoding a class instance.The snippet<?phpclass Example{    private   $privateprop   = "private property";    protected $protectedprop = "protected property";    public    $publicprop    = "public property";}echo json_encode(new Example);?>only returns {"publicprop":"public property"}

here is a small updated version of utf8ize that has the following addition : * It uses iconv instead of utf8_encode for potentially better result.* It adds the support of objects variable * It also update array key value (in a case I met I had to utf8ize the key as well as those were generated from a user input value)Here is the code.<?php    function utf8ize($d) {        if (is_array($d)) {            foreach ($d as $k => $v) {                unset($d[$k]);        $d[utf8ize($k)] = utf8ize($v);            }        } else if (is_object($d)) {        $objVars = get_object_vars($d);        foreach($objVars as $key => $value) {        $d->$key = utf8ize($value);        }            } else if (is_string ($d)) {            return iconv('UTF-8', 'UTF-8//IGNORE', utf8_encode($d));        }         return $d;    }?>