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 程式師世界 >> 編程語言 >> 網頁編程 >> PHP編程 >> PHP綜合 >> php語言中使用json的技巧及json的實現代碼詳解

php語言中使用json的技巧及json的實現代碼詳解

編輯:PHP綜合

目前,JSON已經成為最流行的數據交換格式之一,各大網站的API幾乎都支持它。

我寫過一篇《數據類型和JSON格式》,探討它的設計思想。今天,我想總結一下PHP語言對它的支持,這是開發互聯網應用程序(特別是編寫API)必須了解的知識。

從5.2版本開始,PHP原生提供json_encode()和json_decode()函數,前者用於編碼,後者用於解碼。

一、json_encode()

該函數主要用來將數組和對象,轉換為json格式。先看一個數組轉換的例子:

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

結果為

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

再看一個對象轉換的例子:

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

結果為

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

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

二、索引數組和關聯數組

PHP支持兩種數組,一種是只保存"值"(value)的索引數組(indexed array),另一種是保存"名值對"(name/value)的關聯數組(associative array)。

由於javascript不支持關聯數組,所以json_encode()只將索引數組(indexed array)轉為數組格式,而將關聯數組(associative array)轉為對象格式。

比如,現在有一個索引數組

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

結果為:

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

如果將它改為關聯數組:

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

結果就變了:

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

注意,數據格式從"[]"(數組)變成了"{}"(對象)。

如果你需要將"索引數組"強制轉化成"對象",可以這樣寫

json_encode( (object)$arr );

或者

json_encode ( $arr, JSON_FORCE_OBJECT );

三、類(class)的轉換

下面是一個PHP的類:

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;
    }
}

現在,對這個類的實例進行json轉換:

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

輸出結果是

{"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()

該函數用於將json文本轉換為相應的PHP數據結構。下面是一個例子:

$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,而不是數組。比如:

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

結果就是生成一個PHP對象:

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

如果想要強制生成PHP關聯數組,json_decode()需要加一個參數true:

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

結果就生成了一個關聯數組:

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,你能看出錯在哪裡嗎?

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

對這三個字符串執行json_decode()都將返回null,並且報錯。

第一個的錯誤是,json的分隔符(delimiter)只允許使用雙引號,不能使用單引號。第二個的錯誤是,json名值對的"名"(冒號左邊的部分),任何情況下都必須使用雙引號。第三個的錯誤是,最後一個值之後不能添加逗號(trailing comma)。

另外,json只能用來表示對象(object)和數組(array),如果對一個字符串或數值使用json_decode(),將會返回null。

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

下面給大家介紹哦php語言的json實現

由於開發一個ajax file manager for web開源項目,數據交換使用的json格式,後來發現在低版本的php上運行會有問題,仔細調試發現json_decode和json_encode無法正常工作,於是查閱資料,發現低版本的php沒有實現這兩個函數,為了兼容性,我只好自己實現一個php版的json編碼解碼代碼,並保證和json2.js的一致,測試調試並通過,現在將其公布出來,供有相同需求的同學使用:

<?php 
/* * **************************************************************************** 
 * $base: $ 
 * 
 * $Author: $ 
 *   Berlin Qin 
 * 
 * $History: base.js $ 
 *   Berlin Qin  //     created 
 * 
 * $contacted 
 *   [email protected] 
 *   www.webfmt.com 
 * 
 * *************************************************************************** */ 
/* =========================================================================== 
 * license 
 * 
 * 、Open Source Licenses 
 * webfmt is distributed under the GPL, LGPL and MPL open source licenses. 
 * This triple copyleft licensing model avoids incompatibility with other open source licenses. 
 * These Open Source licenses are specially indicated for: 
 *  Integrating webfmt into Open Source software; 
 *  Personal and educational use of webfmt; 
 *  Integrating webfmt in commercial software, 
 * taking care of satisfying the Open Source licenses terms, 
 *  while not able or interested on supporting webfmt and its development. 
 * 
 * 、Commercial License – fbis source Closed Distribution License - CDL 
 * For many companies and products, Open Source licenses are not an option. 
 * This is why the fbis source Closed Distribution License (CDL) has been introduced. 
 * It is a non-copyleft license which gives companies complete freedom 
 * when integrating webfmt into their products and web sites. 
 * This license offers a very flexible way to integrate webfmt in your commercial application. 
 * These are the main advantages it offers over an Open Source license: 
 *   Modifications and enhancements doesn't need to be released under an Open Source license; 
 *   There is no need to distribute any Open Source license terms alongside with your product 
 * and no reference to it have to be done; 
 *   No references to webfmt have to be done in any file distributed with your product; 
 *   The source code of webfmt doesn't have to be distributed alongside with your product; 
 *   You can remove any file from webfmt when integrating it with your product. 
 * The CDL is a lifetime license valid for all releases of webfmt published during 
 * and before the year following its purchase. 
 * It's valid for webfmt releases also. It includes year of personal e-mail support. 
 * 
 * ************************************************************************************************************************************************* */ 
function jsonDecode($json) 
{ 
  $result = array(); 
  try 
  { 
    if (PHP_VERSION_ID > ) 
    { 
      $result = (array) json_decode($json); 
    } 
    else 
    { 
      $json = str_replace(array("\\\\", "\\\""), array("&#;", "&#;"), $json); 
      $parts = preg_split("@(\"[^\"]*\")|([\[\]\{\},:])|\s@is", $json, -, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE); 
      foreach ($parts as $index => $part) 
      { 
        if (strlen($part) == ) 
        { 
          switch ($part) 
          { 
            case "[": 
            case "{": 
              $parts[$index] = "array("; 
              break; 
            case "]": 
            case "}": 
              $parts[$index] = ")"; 
              break; 
            case ":": 
              $parts[$index] = "=>"; 
              break; 
            case ",": 
              break; 
            default: 
              break; 
          } 
        } 
      } 
      $json = str_replace(array("&#;", "&#;", "$"), array("\\\\", "\\\"", "\\$"), implode("", $parts)); 
      $result = eval("return $json;"); 
    } 
  } 
  catch (Exception $e) 
  { 
    $result = array("error" => $e->getCode()); 
  } 
  return $result; 
} 
function valueTostr($val) 
{ 
  if (is_string($val))  
  { 
    $val = str_replace('\"', "\\\"", $val); 
    $val = str_replace("\\", "\\\\", $val); 
    $val = str_replace("/", "\\/", $val); 
    $val = str_replace("\t", "\\t", $val); 
    $val = str_replace("\n", "\\n", $val); 
    $val = str_replace("\r", "\\r", $val); 
    $val = str_replace("\b", "\\b", $val); 
    $val = str_replace("\f", "\\f", $val); 
    return '"' . $val . '"'; 
  } 
  elseif (is_int($val)) 
    return sprintf('%d', $val); 
  elseif (is_float($val)) 
    return sprintf('%F', $val); 
  elseif (is_bool($val)) 
    return ($val ? 'true' : 'false'); 
  else 
    return 'null'; 
} 
function jsonEncode($arr) 
{ 
  $result = "{}"; 
  try 
  { 
    if (PHP_VERSION_ID > ) 
    { 
      $result = json_encode($arr); 
    } 
    else 
    { 
      $parts = array(); 
      $is_list = false; 
      if (!is_array($arr)) 
      { 
        $arr = (array) $arr; 
      } 
      $end = count($arr) - ; 
      if (count($arr) > ) 
      { 
        if (is_numeric(key($arr))) 
        { 
          $result = "[";  
          for ($i = ; $i < count($arr); $i++) 
          { 
            if (is_array($arr[$i])) 
            { 
              $result = $result . jsonEncode($arr[$i]); 
            } 
            else 
            { 
              $result = $result . valueTostr($arr[$i]); 
            } 
            if ($i != $end) 
            { 
              $result = $result . ","; 
            } 
          } 
          $result = $result . "]"; 
        } 
        else 
        { 
          $result = "{";  
          $i = ; 
          foreach ($arr as $key => $value) 
          { 
            $result = $result . '"' . $key . '":'; 
            if (is_array($value)) 
            { 
              $result = $result . jsonEncode($value); 
            } 
            else 
            { 
              $result = $result . valueTostr($value); 
            } 
            if ($i != $end) 
            { 
              $result = $result . ","; 
            } 
            $i++; 
          } 
          $result = $result . "}"; 
        } 
      } 
      else 
      { 
        $result = "[]"; 
      } 
    } 
  } 
  catch (Exception $e) 
  { 
  } 
  return $result; 
} 
?> 

如果使用過程有什麼問題,可以給我email.歡迎大家指出錯誤!

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