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json_last_error

(PHP 5 >= 5.3.0, PHP 7, PHP 8)

json_last_error返回最后发生的错误

说明

json_last_error(): int

没有指定 JSON_THROW_ON_ERROR时,返回上一次 JSON 编码解码时发生的最后一个错误(如果有)。

参数

此函数没有参数。

返回值

返回一个整型(integer),这个值会是以下的常量之一:

JSON 错误码
常量 含义 可用性
JSON_ERROR_NONE 没有错误发生  
JSON_ERROR_DEPTH 到达了最大堆栈深度  
JSON_ERROR_STATE_MISMATCH 无效或异常的 JSON  
JSON_ERROR_CTRL_CHAR 控制字符错误,可能是编码不对  
JSON_ERROR_SYNTAX 语法错误  
JSON_ERROR_UTF8 异常的 UTF-8 字符,也许是因为不正确的编码。  
JSON_ERROR_RECURSION One or more recursive references in the value to be encoded  
JSON_ERROR_INF_OR_NAN One or more NAN or INF values in the value to be encoded  
JSON_ERROR_UNSUPPORTED_TYPE 指定的类型,值无法编码。  
JSON_ERROR_INVALID_PROPERTY_NAME 指定的属性名无法编码。  
JSON_ERROR_UTF16 畸形的 UTF-16 字符,可能因为字符编码不正确。  

示例

示例 #1 json_last_error() 例子

<?php
// 一个有效的 json 字符串
$json[] = '{"Organization": "PHP Documentation Team"}';

// 一个无效的 json 字符串会导致一个语法错误,在这个例子里我们使用 ' 代替了 " 作为引号
$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;
}
?>

以上示例会输出:

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

示例 #2 json_encode()json_last_error()

<?php
// 无效的 UTF8 序列
$text = "\xB1\x31";

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

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

以上示例会输出:

string(4) "null"
bool(true)

示例 #3 json_last_error()JSON_THROW_ON_ERROR

<?php
// 导致 JSON_ERROR_UTF8 的无效 UTF8 序列
json_encode("\xB1\x31");

// 以下不会导致 JSON 错误
json_encode('okay', JSON_THROW_ON_ERROR);

// 前者的 json_encode() 不会改变全局错误状态
var_dump(json_last_error() === JSON_ERROR_UTF8);
?>

以上示例会输出:

bool(true)

参见

add a note

User Contributed Notes 7 notes

up
317
jimmetry at gmail dot com
12 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
44
praveenscience at gmail dot com
9 years 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
30
hemono at gmail dot com
8 years 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"
up
12
msxcms at bmforum dot com
6 years ago
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;
}
up
9
George Dimitriadis
7 years ago
Just adding this note since I had to code this for the actual values reference.

<?php

echo 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_NONE
1 JSON_ERROR_DEPTH
2 JSON_ERROR_STATE_MISMATCH
3 JSON_ERROR_CTRL_CHAR
4 JSON_ERROR_SYNTAX
5 JSON_ERROR_UTF8
6 JSON_ERROR_RECURSION
7 JSON_ERROR_INF_OR_NAN
8 JSON_ERROR_UNSUPPORTED_TYPE
*/

?>
up
11
williamprogphp at yahoo dot com dot br
10 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
up
1
wedge at atlanteans dot net
6 years ago
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;
}
?>
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