PHP JSON usage examples

1. json_encode()

This function is mainly used to convert arrays and objects into json format. Let’s first look at an example of array conversion:

　 $arr = array ('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5);
　echo json_encode($arr);

The result is

　{"a":1,"b":2,"c":3,"d":4,"e":5}

Let’s look at another example of object conversion:

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

The result is

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

Since JavaScript does not support associative arrays, json_encode() only converts indexed arrays to array format, and converts associative arrays to object format. For example, now there is an index array

　$arr = Array('one', 'two', 'three');

echo json_encode($arr);

　["one","two","three"] 　

　 $arr = Array('1'=>'one', '2'=>'two', '3'=>'three');

　　　　　　　 echo json_encode($arr);　　

 The result changed:

　{"1":"one","2":"two","3":"three"} 　

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

json_encode( (object)$arr );

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 or

json_encode ( $arr, JSON_FORCE_OBJECT );

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class Foo { const ERROR_CODE = '404'; public $public_ex = 'this is public'; private $private_ex = 'this is private!'; protected $protected_ex = 'this should be protected';

　　

　　public function getErrorCode() {　

　　　　return self::ERROR_CODE;　　

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 Now, perform json conversion on the instance of this class: 

　$foo = new Foo;
　$foo_json = json_encode($foo);
　echo $foo_json;

 The output is 

　{"public_ex":"this is public"}

 You can see that except for public variables (public), other things (constants, private variables, methods, etc.) are missing. 
 4. json_decode() 
 This function is used to convert json text into the corresponding PHP data structure. Here is an example: 

　 $json = '{"foo": 12345}';

　 $obj = json_decode($json);


　 $json = '{"a":1,"b":2,"c":3,"d":4,"e":5}'; 　　Copy code



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



　 $json = '{"a":1,"b":2,"c":3,"d":4,"e":5}'; 　　Copy code



　array(5) {　　　　["a"] => int(1)　　["b"] => int(2)　　["c"] => int(3)　　　["d" ] => int(4)　　["e"] => int(5)　Copy code


 The following three ways of writing json are all wrong. Can you see where the error is? 


　$bad_json = "{ 'bar': 'baz' }"; 　$bad_json = '{ bar: "baz" }'; 

 In addition, json can only be used to represent objects and arrays. If json_decode() is used on a string or value, null will be returned. 


　var_dump(json_decode("Hello World")); //null



PHP, JSON