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(PHP 5 >= 5.3.0, PHP 7)
json_last_error — 返回最后发生的错误
如果有,返回 JSON 编码解码时最后发生的错误。
此函数没有参数。
返回一个整型(integer),这个值会是以下的常量之一:
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。 | 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 |
Example #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 ;
}
?>
以上例程会输出:
Decoding: {"Organization": "PHP Documentation Team"} - No errors Decoding: {'Organization': 'PHP Documentation Team'} - Syntax error, malformed JSON
Example #2 json_encode() 的 json_last_error()
<?php
// 无效的 UTF8 序列
$text = "\xB1\x31" ;
$json = json_encode ( $text );
$error = json_last_error ();
var_dump ( $json , $error === JSON_ERROR_UTF8 );
?>
以上例程会输出:
string(4) "null" bool(true)
[#1] hemono at gmail dot com [2015-10-18 15:02:23]
when json_decode a empty string, PHP7 will trigger an Syntax error:
<?php
json_decode("");
var_dump(json_last_error(), json_last_error_msg());
// PHP 7
int(4)
string(12) "Syntax error"
// PHP 5
int(0)
string(8) "No error"
[#2] qrworld.net [2014-11-07 10:15:44]
I found a full article about json_last_error and json_last_error_msg that shows the result depending on the fact that exists or not the functions due to the PHP version.
In this url you have this full article: http://softontherocks.blogspot.com/2014/11/funcion-jsonlasterror-y.html
[#3] praveenscience at gmail dot com [2014-10-21 15:17:22]
I used this simple script, flicked from StackOverflow to escape from the function failing:
<?php
function utf8ize($d) {
if (is_array($d)) {
foreach ($d as $k => $v) {
$d[$k] = utf8ize($v);
}
} else if (is_string ($d)) {
return utf8_encode($d);
}
return $d;
}
?>
Cheers,
Praveen Kumar!
[#4] williamprogphp at yahoo dot com dot br [2014-01-30 18:32:09]
This is a quite simple and functional trick to validate JSON's strings.
<?php
function json_validate($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
[#5] jimmetry at gmail dot com [2011-11-23 21:16:31]
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.
[#6] lior at mytopia dot com [2009-03-09 05:17:14]
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;
}
}
?>