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Home php教程 php手冊 php中JSON的使用與轉(zhuǎn)換

php中JSON的使用與轉(zhuǎn)換

Jun 06, 2016 pm 08:14 PM
json php use Convert

這篇文章主要介紹了php中JSON的使用與轉(zhuǎn)換,講解的十分細(xì)致全面,是篇非常不錯的文章,需要的朋友可以參考下

在之前我寫過php返回json數(shù)據(jù)簡單實(shí)例,剛剛上網(wǎng),突然發(fā)現(xiàn)一篇文章,也是介紹json的,還挺詳細(xì),值得參考。內(nèi)容如下

從5.2版本開始,PHP原生提供json_encode()和json_decode()函數(shù),前者用于編碼,后者用于解碼。

一、json_encode()

復(fù)制代碼 代碼如下:


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

輸出

復(fù)制代碼 代碼如下:


{"a":1,"b":2,"c":3,"d":4,"e":5}

再看一個對象轉(zhuǎn)換的例子:

復(fù)制代碼 代碼如下:


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

?輸出

復(fù)制代碼 代碼如下:


{
   "body":"another post",
   "id":21,
   "approved":true,
   "favorite_count":1,
   "status":null
 }

?由于json只接受utf-8編碼的字符,所以json_encode()的參數(shù)必須是utf-8編碼,否則會得到空字符或者null。當(dāng)中文使用GB2312編碼,或者外文使用ISO-8859-1編碼的時候,這一點(diǎn)要特別注意。

二、索引數(shù)組和關(guān)聯(lián)數(shù)組

PHP支持兩種數(shù)組,一種是只保存"值"(value)的索引數(shù)組(indexed array),另一種是保存"名值對"(name/value)的關(guān)聯(lián)數(shù)組(associative array)。

由于javascript不支持關(guān)聯(lián)數(shù)組,所以json_encode()只將索引數(shù)組(indexed array)轉(zhuǎn)為數(shù)組格式,而將關(guān)聯(lián)數(shù)組(associative array)轉(zhuǎn)為對象格式。

比如,現(xiàn)在有一個索引數(shù)組

復(fù)制代碼 代碼如下:


$arr = Array('one', 'two', 'three');
echo json_encode($arr);

?輸出

復(fù)制代碼 代碼如下:


["one","two","three"]

?如果將它改為關(guān)聯(lián)數(shù)組:

復(fù)制代碼 代碼如下:


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

?輸出變?yōu)?/p>

復(fù)制代碼 代碼如下:


{"1":"one","2":"two","3":"three"}

?注意,數(shù)據(jù)格式從"[]"(數(shù)組)變成了"{}"(對象)。

如果你需要將"索引數(shù)組"強(qiáng)制轉(zhuǎn)化成"對象",可以這樣寫

復(fù)制代碼 代碼如下:


json_encode( (object)$arr );

?或者

復(fù)制代碼 代碼如下:


json_encode ( $arr, JSON_FORCE_OBJECT );

?三、類(class)的轉(zhuǎn)換

下面是一個PHP的類:

復(fù)制代碼 代碼如下:


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;
  }
}

?現(xiàn)在,對這個類的實(shí)例進(jìn)行json轉(zhuǎn)換:

復(fù)制代碼 代碼如下:


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

?輸出結(jié)果是

復(fù)制代碼 代碼如下:


{"public_ex":"this is public"}

?可以看到,除了公開變量(public),其他東西(常量、私有變量、方法等等)都遺失了。

四、json_decode()

該函數(shù)用于將json文本轉(zhuǎn)換為相應(yīng)的PHP數(shù)據(jù)結(jié)構(gòu)。下面是一個例子:

復(fù)制代碼 代碼如下:


$json = '{"foo": 12345}';
$obj = json_decode($json);
print $obj->{'foo'}; // 12345

?通常情況下,json_decode()總是返回一個PHP對象,而不是數(shù)組。比如:

復(fù)制代碼 代碼如下:


$json = '{"a":1,"b":2,"c":3,"d":4,"e":5}';
var_dump(json_decode($json));

?結(jié)果就是生成一個PHP對象:

復(fù)制代碼 代碼如下:


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

?如果想要強(qiáng)制生成PHP關(guān)聯(lián)數(shù)組,json_decode()需要加一個參數(shù)true:

復(fù)制代碼 代碼如下:


$json = '{"a":1,"b":2,"c":3,"d":4,"e":5}'; 
 var_dump(json_decode($json,true));

?結(jié)果就生成了一個關(guān)聯(lián)數(shù)組:

復(fù)制代碼 代碼如下:


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

五、json_decode()的常見錯誤

下面三種json寫法都是錯的,你能看出錯在哪里嗎?

復(fù)制代碼 代碼如下:


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

?對這三個字符串執(zhí)行json_decode()都將返回null,并且報錯。

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