json_decode()

(PHP 5 >= 5.2.0, PHP 7, PECL json >= 1.2.0)

对 JSON 格式的字符串进行解码

说明

接受一个 JSON 编码的字符串并且把它转换为 PHP 变量

参数

待解码的$jsonstring格式的字符串。

这个函数仅能处理 UTF-8 编码的数据。

PHP implements a superset of JSON as specified in the original » RFC 7159.$assoc

当该参数为TRUE时，将返回array而非object。

指定递归深度。

由JSON_BIGINT_AS_STRING,JSON_INVALID_UTF8_IGNORE,JSON_INVALID_UTF8_SUBSTITUTE,JSON_OBJECT_AS_ARRAY,JSON_THROW_ON_ERROR组成的掩码。这些常量的行为在JSON constants页面有进一步描述。

返回值

通过恰当的 PHP 类型返回在$json中编码的数据。值true,false和null会相应地返回TRUE,FALSE和NULL。如果$json无法被解码，或者编码数据深度超过了递归限制的话，将会返回NULL。

更新日志

范例

json_decode()的例子

以上例程会输出：

object(stdClass)#1 (5) {
    ["a"] => int(1)
    ["b"] => int(2)
    ["c"] => int(3)
    ["d"] => int(4)
    ["e"] => int(5)
}
array(5) {
    ["a"] => int(1)
    ["b"] => int(2)
    ["c"] => int(3)
    ["d"] => int(4)
    ["e"] => int(5)
}

Accessing invalid object properties

Accessing elements within an object that contain characters not permitted under PHP's naming convention(e.g. the hyphen)can be accomplished by encapsulating the element name within braces and the apostrophe.

common mistakes using json_decode()

Example #4$deptherrors

以上例程会输出：

array(1) {
  [1]=>
  array(2) {
    ["English"]=>
    array(2) {
      [0]=>
      string(3) "One"
      [1]=>
      string(7) "January"
    }
    ["French"]=>
    array(2) {
      [0]=>
      string(3) "Une"
      [1]=>
      string(7) "Janvier"
    }
  }
}
Last error: JSON_ERROR_NONE
NULL
Last error: JSON_ERROR_DEPTH

json_decode() of large integers

以上例程会输出：

object(stdClass)#1 (1) {
  ["number"]=>
  float(1.2345678901235E+19)
}
object(stdClass)#1 (1) {
  ["number"]=>
  string(20) "12345678901234567890"
}

注释

The JSON spec is not JavaScript, but a subset of JavaScript.Note:

In the event of a failure to decode,json_last_error() can be used to determine the exact nature of the error.

参见

• json_encode()对变量进行 JSON 编码
• json_last_error()返回最后发生的错误

Make sure you pass in utf8 content, or json_decode may error out and just return a null value. For a particular web service I was using, I had to do the following:

Hope this helps!

The function by 1franck to allow comments works except if there is a comment at the very beginning of the file. Here's a modified version (only the regex was changed) that accounts for that. 

First of all, since JSON is not native PHP format or even native JavaScript format, everyone who wants to use JSON wisely should carefuly read official documentation. There is a link to it here, in "Introduction" section. Many questions like "it doesn't recognize my strings" and those like previous one (about zip codes) will drop if you will be attentive!
And second. I've found that there is no good, real working example of how to validate string if it is a JSON or not.
There are two ways to make this: parse input string for yourself using regular expressions or anything else, use json_decode to do it for you.
Parsing for yourself is like writing your own compiler, too difficult.
Just testing result of json_decode is not enough because you should test it with NULL, but valid JSON could be like this 'null' and it will evaluate to NULL. So you should use another function - json_last_error. It will return error code of the last encode/decode operation. If no error occured it will be JSON_ERROR_NONE. So here is the function you should use for testing:

It's so simple, that there is no need to use it and slow down your script with extra delay for function call. Just do it manualy in you code while working with input data: 

When decoding strings from the database, make sure the input was encoded with the correct charset when it was input to the database.
I was using a form to create records in the DB which had a content field that was valid JSON, but it included curly apostrophes. If the page with the form did not have 

in the head, then the data was sent to the database with the wrong encoding. Then, when json_decode tried to convert the string to an object, it failed every time.

Sometime, i need to allow comments in json file. So i wrote a small func to clean comments in a json string before decoding it: 

it seems, that some of the people are not aware, that if you are using json_decode to decode a string it HAS to be a propper json string:

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