PHP Json_decode and Json_encode use method sharing

Json_decode and Json_encode are JSON strings, this article is mainly to share with you in PHP Json_decode and Json_encode use method, I hope to help everyone.

First, Json_encode ()

This function is primarily used to convert arrays and objects into JSON format. Let's look at an example of an array conversion:

$arr = Array (' A ' =>1, ' B ' =>2, ' C ' =>3, ' d ' =>4, ' e ' =>5); echo Json_encode ($arr);

Result is

{"A": 1, "B": 2, "C": 3, "D": 4, "E": 5}

Let's look at an example of an object conversion:

$obj->body      = ' another post ';　　$obj->id       = 21;　　$obj->approved    = true;　　$obj->favorite_count = 1;　　$obj->status     = NULL; echo Json_encode ($obj);

Result is

{    "body": "Another Post", "id": +, "approved": True, "Favorite_count": 1, "status": null}

Because JSON accepts only utf-8 encoded characters, the Json_encode () argument must be utf-8 encoded, otherwise it will get a null character or null. This is especially important when using GB2312 encoding in Chinese, or when using ISO-8859-1 encoding in a foreign language.

indexed arrays and associative arrays

PHP supports two arrays, one is an indexed array (indexed array) that only holds "value", and the other is an associative array (associative array) that holds "name value pairs" (name/value).

Because JavaScript does not support associative arrays, json_encode () only converts an indexed array (indexed array) into an array format, and the associative array (associative array) to the object format.

For example, there is now an indexed array

$arr = Array (' One ', ' one ', ' one ', ' three '); echo Json_encode ($arr);

The result is:

["One", "one", "three"]

If you change it to an associative array:

$arr = Array (' 1 ' = ' one ', ' 2 ' = '-'-', ' 3 ' = ' three '); Echo Json_encode ($arr);

The result is changed:

{"1": "One", "2": "One", "3": "Three"}

Note that the data format has changed from "[]" (array) to "{}" (object).

If you need to force an "indexed array" into an "object", you can write

Json_encode ((object) $arr);

Or

Json_encode ($arr, json_force_object);

Classes (Class) conversions

The following is a PHP class:

Class Foo {const   error_code = ' 404 ';　　　　　　Public  $public _EX = ' the public ';　　　　　　Private  $private _ex = ' this is private! ';　　　　　　protected $protected _EX = ' This should is protected ';  Public Function GetErrorCode () {return self::error_code; }　　　　}

Now, JSON transforms the instance of this class:

$foo = new Foo;　　$foo _json = Json_encode ($foo); echo $foo _json;

The output is

{"PUBLIC_EX": "This was public"}

As you can see, other things (constants, private variables, methods, and so on) are lost in addition to the public variables.

Second, Json_decode ()

This function is used to convert the JSON text to the appropriate PHP data structure. Here is an example:

$json = ' {' foo ': 12345} ';　　$obj = Json_decode ($json); Print $obj->{' foo '}; 12345

Typically, Json_decode () always returns a PHP object instead of an array. Like what:

$json = ' {' A ': 1, ' B ': 2, ' C ': 3, ' d ': 4, ' E ': 5} '; Var_dump (Json_decode ($json));

The result is to generate a PHP object:

Object (StdClass) #1 (5) {["a"] + int (1) ["b"] = + int (2) ["c"] = = Int (3) ["D"] + int (4) ["E"] = = Int (5)}

If you want to force a PHP associative array to be generated, json_decode () needs to add a parameter of true:

$json = ' {' A ': 1, ' B ': 2, ' C ': 3, ' d ': 4, ' E ': 5} '; Var_dump (Json_decode ($json, true));

As a result, an associative array is generated:

Array (5) {["a"] + int (1) ["b"] = + int (2) ["C"] + int (3) ["D"] = + int (4) ["e"] = int (5)}

Common errors in Json_decode ()

The following three kinds of JSON notation are wrong, can you see where is wrong?

$bad _json = "{' Bar ': ' Baz '}";　　$bad _json = ' {bar: ' Baz '} '; $bad _json = ' {' bar ': ' Baz ', '} ';

Executing Json_decode () on these three strings will return null and error.

The first error is that the JSON delimiter (delimiter) only allows double quotation marks and cannot use single quotes. The second error is the "name" of the JSON name-value pair (the left part of the colon), which must use double quotes in any case. The third error is that you cannot add a comma after the last value (trailing comma).

In addition, JSON can only be used to represent objects (object) and Arrays (array), and if you use Json_decode () for a string or numeric value, NULL will be returned.

Third, JavaScript uses JSON strings

Methods of converting JSON strings to JSON objects

Use the following method to first convert to a JSON object:

Converted from a JSON string to a JSON object var obj = eval (' (' + str + ') ');

Or

var obj = Str.parsejson (); Convert from JSON string to JSON object

Or

var obj = json.parse (str); Convert from JSON string to JSON object

Then, you can read this:

Alert (Obj.name); Alert (Obj.sex);

Special Note: If obj is originally a JSON object, then using the eval () function after conversion (even if multiple conversions) is a JSON object, but there is a problem with the Parsejson () function (throwing a syntax exception).