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php语言中使用json的技巧及json的实现代码详解

时间:2021-07-01 10:21:17 帮助过:7人阅读

目前,JSON已经成为最流行的数据交换格式之一,各大网站的API几乎都支持它。

我写过一篇《数据类型和JSON格式》,探讨它的设计思想。今天,我想总结一下PHP语言对它的支持,这是开发互联网应用程序(特别是编写API)必须了解的知识。

从5.2版本开始,PHP原生提供json_encode()和json_decode()函数,前者用于编码,后者用于解码。

一、json_encode()

该函数主要用来将数组和对象,转换为json格式。先看一个数组转换的例子:

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

结果为

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

再看一个对象转换的例子:

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

结果为

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

由于json只接受utf-8编码的字符,所以json_encode()的参数必须是utf-8编码,否则会得到空字符或者null。当中文使用GB2312编码,或者外文使用ISO-8859-1编码的时候,这一点要特别注意。

二、索引数组和关联数组

PHP支持两种数组,一种是只保存"值"(value)的索引数组(indexed array),另一种是保存"名值对"(name/value)的关联数组(associative array)。

由于javascript不支持关联数组,所以json_encode()只将索引数组(indexed array)转为数组格式,而将关联数组(associative array)转为对象格式。

比如,现在有一个索引数组

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

结果为:

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

如果将它改为关联数组:

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

结果就变了:

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

注意,数据格式从"[]"(数组)变成了"{}"(对象)。

如果你需要将"索引数组"强制转化成"对象",可以这样写

json_encode( (object)$arr );

或者

json_encode ( $arr, JSON_FORCE_OBJECT );

三、类(class)的转换

下面是一个PHP的类:

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;
    }
}

现在,对这个类的实例进行json转换:

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

输出结果是

{"public_ex":"this is public"}

可以看到,除了公开变量(public),其他东西(常量、私有变量、方法等等)都遗失了。

四、json_decode()

该函数用于将json文本转换为相应的PHP数据结构。下面是一个例子:

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

通常情况下,json_decode()总是返回一个PHP对象,而不是数组。比如:

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

结果就是生成一个PHP对象:

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

如果想要强制生成PHP关联数组,json_decode()需要加一个参数true:

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

结果就生成了一个关联数组:

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

五、json_decode()的常见错误

下面三种json写法都是错的,你能看出错在哪里吗?

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

对这三个字符串执行json_decode()都将返回null,并且报错。

第一个的错误是,json的分隔符(delimiter)只允许使用双引号,不能使用单引号。第二个的错误是,json名值对的"名"(冒号左边的部分),任何情况下都必须使用双引号。第三个的错误是,最后一个值之后不能添加逗号(trailing comma)。

另外,json只能用来表示对象(object)和数组(array),如果对一个字符串或数值使用json_decode(),将会返回null。

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

下面给大家介绍哦php语言的json实现

由于开发一个ajax file manager for web开源项目,数据交换使用的json格式,后来发现在低版本的php上运行会有问题,仔细调试发现json_decode和json_encode无法正常工作,于是查阅资料,发现低版本的php没有实现这两个函数,为了兼容性,我只好自己实现一个php版的json编码解码代码,并保证和json2.js的一致,测试调试并通过,现在将其公布出来,供有相同需求的同学使用:

<?php 
/* * **************************************************************************** 
 * $base: $ 
 * 
 * $Author: $ 
 *   Berlin Qin 
 * 
 * $History: base.js $ 
 *   Berlin Qin  //     created 
 * 
 * $contacted 
 *   webfmt@gmail.com 
 *   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; 
} 
?> 

如果使用过程有什么问题,可以给我email.欢迎大家指出错误!

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