爲什麼json_decode爲空數組返回null？

爲什麼會回顯「NULL」？在我的意志它將被解碼爲一個空的數組。爲什麼json_decode爲空數組返回null？

我錯過了什麼東西？

<?php 

$json = json_encode(array()); 
$json_decoded = json_decode($json, true); 
// same with json_decode($json); 

if ($json_decoded == null){ 
    echo "NULL"; 
} else 
{ 
    echo "NOT NULL"; 
} 

?>

來源

2012-06-13 netigger

如果您嘗試'$ json_decoded === null'，該怎麼辦？ – mgraph

@Aelios：PHP中的數組沒有'new'關鍵字。 – prodigitalson

你曾期待回報不同的東西？ – Sena

這是因爲array()==NULL。在這種情況下它不檢查對象類型。

gettype(null)返回NULL，而

gettype(array())返回陣列。希望你有所作爲。

也許你需要的是

if ($json_decoded === null) { 
    echo "NULL"; 
} else 
{ 
    echo "NOT NULL"; 
}

來源

2012-06-13 11:26:49 gopi1410

這必須從manual做的伎倆

if ($json_decoded === null)

實施例：

<?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"; 
?>

輸出：

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"}

來源

2012-06-13 11:26:25 greenLizard

的print_r的$ json_decoded值它給空數組回來。 :)

$json = json_encode(array()); 
$json_decoded = json_decode($json, true); 


if ($json_decoded == null){ 
    print_r($json_decoded); 
} else 
{ 
    echo "NOT NULL"; 
}

輸出：陣列（） 這是因爲==操作符的空數組被篡改鍵入爲空

來源

2012-06-13 11:27:43 mithunsatheesh

您需要使用全等運算符===，觀察自己：

$json = json_encode(array()); 
var_dump($json); // string(2) "[]" 
$json_decoded = json_decode($json, true); 
var_dump($json_decoded); // array(0) { }

這樣算下來：

$json = json_encode(array()); 
$json_decoded = json_decode($json, true); 

if ($json_decoded === null) 
{ 
    echo "NULL"; 
} else 
{ 
    echo "NOT NULL"; 
}

將在else條件打印NOT NULL

來源

2012-06-13 11:28:51 Sarfraz

正確地去如果你的數據包括一些\n json_decode可能靜默失敗了。

來源

2013-04-30 22:46:10 Hafenkranich

爲什麼json_decode爲空數組返回null？

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