php中json_decode()和json_encode()的使用方法

1.json_decode() 

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

json_decode — 對 JSON 格式的字符串進行編碼 

說明 
mixed json_decode ( string $json [, bool $assoc ] ) 
接受一個 JSON 格式的字符串並且把它轉換爲 PHP 變量 

參數 

json 
待解碼的 json string 格式的字符串。 

assoc 
當該參數爲 TRUE 時，將返回 array 而非 object 。 


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

範例 

Example #1 json_decode() 的例子 

複製代碼代碼如下:

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

上例將輸出： 

複製代碼代碼如下:

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

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

複製代碼代碼如下:

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

結果爲： 

複製代碼代碼如下:

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] => ) ) 

可以看出經過json_decode()編譯出來的是對象,現在輸出json_decode($data,true)試下 

複製代碼代碼如下:

echo json_decode($data,true); 

結果： 

複製代碼代碼如下:

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($data,true)輸出的一個關聯數組,由此可知json_decode($data）輸出的是對象,而json_decode("$arr",true)是把它強制生成PHP關聯數組. 

2.json_encode() 

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

json_encode — 對變量進行 JSON 編碼 

Report a bug 說明 
string json_encode ( mixed $value [, int $options = 0 ] ) 
返回 value 值的 JSON 形式 

Report a bug 參數 

value 
待編碼的 value ，除了resource 類型之外，可以爲任何數據類型 

該函數只能接受 UTF-8 編碼的數據 

options 
由以下常量組成的二進制掩碼： 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 
編碼成功則返回一個以 JSON 形式表示的 string 或者在失敗時返回 FALSE 。 

Report a bug 更新日誌 
版本 說明 
5.4.0 options 參數增加常量： JSON_PRETTY_PRINT, JSON_UNESCAPED_SLASHES, 和 JSON_UNESCAPED_UNICODE。 
5.3.3 options 參數增加常量：JSON_NUMERIC_CHECK。 
5.3.0 增加 options 參數. 


Report a bug 範例 

Example #1 A json_encode() 的例子 

複製代碼代碼如下:

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

echo json_encode($arr); 
?> 

以上例程會輸出： 

複製代碼代碼如下:

{"a":1,"b":2,"c":3,"d":4,"e":5} 

Example #2 json_encode() 函數中 options 參數的用法 

複製代碼代碼如下:

<?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"; 
?> 

以上例程會輸出： 

複製代碼代碼如下:

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 連續與非連續數組示例 

複製代碼代碼如下:

<?php 
echo "連續數組".PHP_EOL; 
$sequential = array("foo", "bar", "baz", "blong"); 
var_dump( 
$sequential, 
json_encode($sequential) 
); 

echo PHP_EOL."非連續數組".PHP_EOL; 
$nonsequential = array(1=>"foo", 2=>"bar", 3=>"baz", 4=>"blong"); 
var_dump( 
$nonsequential, 
json_encode($nonsequential) 
); 

echo PHP_EOL."刪除一個連續數組值的方式產生的非連續數組".PHP_EOL; 
unset($sequential[1]); 
var_dump( 
$sequential, 
json_encode($sequential) 
); 
?> 

以上例程會輸出： 

複製代碼代碼如下:

連續數組 
array(4) { 
[0]=> 
string(3) "foo" 
[1]=> 
string(3) "bar" 
[2]=> 
string(3) "baz" 
[3]=> 
string(5) "blong" 
} 
string(27) "["foo","bar","baz","blong"]" 

非連續數組 
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"}" 

刪除一個連續數組值的方式產生的非連續數組 
array(3) { 
[0]=> 
string(3) "foo" 
[2]=> 
string(3) "baz" 
[3]=> 
string(5) "blong" 
} 
string(33) "{"0":"foo","2":"baz","3":"blong"}" 

複製代碼代碼如下:

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

結果爲： 

複製代碼代碼如下:

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

可以看出json_encode()和json_decode()是編譯和反編譯過程，注意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。