1.json_decode() 
(PHP 5 >= 5.2.0, PECL json >= 1.2.0) 
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 

php"><?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：

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) 
} 

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

结果为： 

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 

echo json_decode($data,true); 

结果如下：

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.。

---

2.json_encode() 
(PHP 5 >= 5.2.0, PECL json >= 1.2.0) 
— 对变量进行 JSON 编码 

说明：
string json_encode ( mixed $value [, int $options = 0 ] ) 
返回 value 值的 JSON 形式 

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. 

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 。 

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.

范例：
Example #1 json_encode() 的例子

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

echo json_encode($arr); 
?>

以上例程会输出： 

{"a":1,"b":2,"c":3,"d":4,"e":5} 

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

<?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： 

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 

<?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：

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"}" 

$obj->Name= 'a1';$obj->Number ='123'; 
$obj->Contno= '000'; 
echo json_encode($obj);

结果为： 

{"Name":"a1", 
"Number":"123", 
"Contno":"000" 
} 

可以看出json_encode()和json_decode()是编译和反编译过程，注意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。