PHP JSON usage examples

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); Copy Code Result is {"A": 1, "B": 2, "C": 3, "D": 4, "E": 5} Copy Code 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); Copy Code Result is {"Body": "Another Post", "id": 21, "Approved": TRUE, "Favorite_count": 1, "Status": null} Copy Code 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. second, 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); Copy Code The result is: ["One", "one", "three"] Copy Code If you change it to an associative array: $arr = Array (' 1 ' = ' one ', ' 2 ' = '-'-', ' 3 ' = ' three '); 　　 echo Json_encode ($arr); Copy Code The result is changed: {"1": "One", "2": "One", "3": "Three"} Copy Code 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) $arr); Copy Code Or Json_encode ($arr, json_force_object); Copy Code Iii. Conversion of classes (class) 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; } } Copy Code Now, JSON transforms the instance of this class: $foo = new Foo; $foo _json = Json_encode ($foo); echo $foo _json; Copy Code The output is {"PUBLIC_EX": "This was public"} Copy Code As you can see, other things (constants, private variables, methods, and so on) are lost in addition to the public variables. iv. 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 Copy Code 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)); Copy Code 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) } Copy Code 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)); Copy Code 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) } Copy Code v. 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 ', '} '; Copy Code 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. Var_dump (Json_decode ("Hello World")); Null Copy Code

PHP, JSON

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