在php中json_encode与json_decode的使用方法

    首先要了解的就是json_encode与json_decode分别在PHP中是干什么的，有什么作用。

        json_decode对JSON格式的字符串进行编码而json_encode对变量进行 JSON 编码

那下面就会更加详细的说一下json_encode与json_decode的用法：

      1.json_encode()

       json_encode

       (PHP 5 >= 5.2.0, PECL json >= 1.2.0)

       json_encode — 对变量进行 JSON 编码

       Report a bug 说明

       string json_encode ( mixed $value [, int $options = 0 ] )

       返回 value 值的 JSON 形式

       Report a bug 参数

       value

       待编码的 value ，除了resource 类型之外，可以为任何数据类型

       该函数只能接受 UTF-8 编码的数据

       options

       由以下常量组成的二进制掩码： JSON_HEX_QUOT, JSON_HEX_TAG, JSON_HEX_AMP, JSON_HEX_APOS,     JSON_NUMERIC_CHECK, JSON_PRETTY_PRINT, JSON_UNESCAPED_SLASHES, JSON_FORCE_OBJECT, JSON_UNESCAPED_UNICODE.

       Report a bug 返回值

       编码成功则返回一个以 JSON 形式表示的 string 或者在失败时返回 FALSE 。

       Report a bug 更新日志

       版本 说明

       5.4.0 options 参数增加常量： JSON_PRETTY_PRINT, JSON_UNESCAPED_SLASHES, 和       JSON_UNESCAPED_UNICODE。

       5.3.3 options 参数增加常量：JSON_NUMERIC_CHECK。

       5.3.0 增加 options 参数.

       Report a bug 范例

       Example #1 A json_encode() 的例子

       复制代码 代码如下:

              <?php

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

               echo json_encode($arr);

               ?>

               以上例程会输出：

               复制代码   代码如下:

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

             Example #2 json_encode() 函数中 options 参数的用法

             复制代码 代码如下:

            <?php

            $a = array('<foo>',"'bar'",'"baz"','&blong&', "\xc3\xa9");

            echo "Normal: ", json_encode($a), "\n";

            echo "Tags: ", json_encode($a, JSON_HEX_TAG), "\n";

            echo "Apos: ", json_encode($a, JSON_HEX_APOS), "\n";

            echo "Quot: ", json_encode($a, JSON_HEX_QUOT), "\n";

            echo "Amp: ", json_encode($a, JSON_HEX_AMP), "\n";

            echo "Unicode: ", json_encode($a, JSON_UNESCAPED_UNICODE), "\n";

            echo "All: ", json_encode($a, JSON_HEX_TAG | JSON_HEX_APOS | JSON_HEX_QUOT | JSON_HEX_AMP | JSON_UNESCAPED_UNICODE), "\n\n";

            $b = array();

            echo "Empty array output as array: ", json_encode($b), "\n";

            echo "Empty array output as object: ", json_encode($b, JSON_FORCE_OBJECT), "\n\n";

            $c = array(array(1,2,3));

            echo "Non-associative array output as array: ", json_encode($c), "\n";

            echo "Non-associative array output as object: ", json_encode($c, JSON_FORCE_OBJECT), "\n\n";

            $d = array('foo' => 'bar', 'baz' => 'long');

             echo "Associative array always output as object: ", json_encode($d), "\n";

             echo "Associative array always output as object: ", json_encode($d, JSON_FORCE_OBJECT), "\n\n";

             ?>

              以上例程会输出：

              复制代码  代码如下:

Normal: ["<foo>","'bar'","\"baz\"","&blong&","\u00e9"]

Tags: ["\u003Cfoo\u003E","'bar'","\"baz\"","&blong&","\u00e9"]

Apos: ["<foo>","\u0027bar\u0027","\"baz\"","&blong&","\u00e9"]

Quot: ["<foo>","'bar'","\u0022baz\u0022","&blong&","\u00e9"]

Amp: ["<foo>","'bar'","\"baz\"","\u0026blong\u0026","\u00e9"]

Unicode: ["<foo>","'bar'","\"baz\"","&blong&","é"]

All: ["\u003Cfoo\u003E","\u0027bar\u0027","\u0022baz\u0022","\u0026blong\u0026","é"]

Empty array output as array: []

Empty array output as object: {}

Non-associative array output as array: [[1,2,3]]

Non-associative array output as object: {"0":{"0":1,"1":2,"2":3}}

Associative array always output as object: {"foo":"bar","baz":"long"}

Associative array always output as object: {"foo":"bar","baz":"long"}

            Example #3 连续与非连续数组示例

            复制代码 代码如下:

<?php

echo "连续数组".PHP_EOL;

$sequential = array("foo", "bar", "baz", "blong");

var_dump(

$sequential,

json_encode($sequential)

);

echo PHP_EOL."非连续数组".PHP_EOL;

$nonsequential = array(1=>"foo", 2=>"bar", 3=>"baz", 4=>"blong");

var_dump(

$nonsequential,

json_encode($nonsequential)

);

echo PHP_EOL."删除一个连续数组值的方式产生的非连续数组".PHP_EOL;

unset($sequential[1]);

var_dump(

$sequential,

json_encode($sequential)

);

?>

以上例程会输出：

复制代码   代码如下:

连续数组
array(4) {

[0]=>

string(3) "foo"

[1]=>

string(3) "bar"

[2]=>

string(3) "baz"

[3]=>

string(5) "blong"

}

string(27) "["foo","bar","baz","blong"]"

非连续数组
array(4) {

[1]=>

string(3) "foo"

[2]=>

string(3) "bar"

[3]=>

string(3) "baz"

[4]=>

string(5) "blong"

}

string(43) "{"1":"foo","2":"bar","3":"baz","4":"blong"}"

删除一个连续数组值的方式产生的非连续数组
array(3) {

[0]=>

string(3) "foo"

[2]=>

string(3) "baz"

[3]=>

string(5) "blong"

}

string(33) "{"0":"foo","2":"baz","3":"blong"}"

复制代码 代码如下:

$obj->Name= 'a1';$obj->Number ='123';

$obj->Contno= '000';

echo json_encode($obj);

结果为：

复制代码   代码如下:

{"Name":"a1",

"Number":"123",

"Contno":"000"

}

2.json_decode()

json_decode

(PHP 5 >= 5.2.0, PECL json >= 1.2.0)

json_decode — 对 JSON 格式的字符串进行编码

说明

mixed json_decode ( string $json [, bool $assoc ] )

接受一个 JSON 格式的字符串并且把它转换为 PHP 变量

参数

json

待解码的 json string 格式的字符串。

assoc

当该参数为 TRUE 时，将返回 array 而非 object 。

返回值

Returns an object or if the optional assoc parameter is TRUE, an associative array is instead returned.

范例

Example #1 json_decode() 的例子

复制代码 代码如下:

<?php

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

var_dump(json_decode($json));

var_dump(json_decode($json, true));

?>

上例将输出：
复制代码   代码如下:

object(stdClass)#1 (5) {

["a"] => int(1)

["b"] => int(2)

["c"] => int(3)

["d"] => int(4)

["e"] => int(5)

}

array(5) {

["a"] => int(1)

["b"] => int(2)

["c"] => int(3)

["d"] => int(4)

["e"] => int(5)

}

复制代码 代码如下:

$data='[{"Name":"a1","Number":"123","Contno":"000","QQNo":""},{"Name":"a1","Number":"123","Contno":"000","QQNo":""},{"Name":"a1","Number":"123","Contno":"000","QQNo":""}]';

echo json_decode($data);

结果为：
复制代码  代码如下:

Array ( [0] => stdClass Object ( [Name] => a1 [Number] => 123 [Contno] => 000 [QQNo] => ) [1] => stdClass Object ( [Name] => a1 [Number] => 123 [Contno] => 000 [QQNo] => ) [2] => stdClass Object ( [Name] => a1
[Number] => 123 [Contno] => 000 [QQNo] => ) )

可以看出经过json_decode()编译出来的是对象,现在输出json_decode($data,true)试下

复制代码 代码如下:

echo json_decode($data,true);

结果：
复制代码 代码如下:

Array ( [0] => Array ( [Name] => a1 [Number] => 123 [Contno] => 000 [QQNo] => ) [1] => Array ( [Name] => a1 [Number] => 123 [Contno] => 000 [QQNo] => ) [2] => Array ( [Name] => a1 [Number] => 123 [Contno] => 000
[QQNo] => ) )

可以看出 json_decode($data,true)输出的一个关联数组,由此可知json_decode($data）输出的是对象,而json_decode("$arr",true)是把它强制生成PHP关联数组.

    好啦，到现在，已经基本完成了json_encode与json_decode的用法啦，学习php还需要大家去多练习练习，多总经经验