blocks|key|320886|text|为此，请使用array_key_exists()和is_null()。如果键存在并且值远离NULL，它将返回TRUE|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|320887|区别：|320888|$arr+=+array('a'+=>+NULL);

var_dump(array_key_exists('a',+$arr));+//+-->++TRUE
var_dump(isset($arr['a']));+//+-->++FALSE|code-block|syntax|javascript|320889|所以你应该检查一下：|320890|if(array_key_exists($key,+$array)+&&+is_null($array[$key]))+{
++++echo+"key+exists+with+a+value+of+NULL";
}|320891|entityMap|0|LINK|mutability|MUTABLE|url|http://www.php.net/manual/en/function.array-key-exists.php|1|http://de2.php.net/manual/en/function.is-null.php^0|6|I|P|9|19|4|1I|4|6|I|0|P|9|1|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]|$9|17|A|18|B|C]]|D|@$9|19|A|1A|1|1B]|$9|1C|A|1D|1|1E]]|E|$]]|$1|F|3|G|5|6|7|1F|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|1G|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1H|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|1I|8|@]|D|@]|E|$K|L]]|$1|Q|3|-4|5|6|7|1J|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]|Y|$5|T|U|V|E|$W|Z]]]]

use <a href="http://www.php.net/manual/en/function.array-key-exists.php" rel="noreferrer"><code>array_key_exists()</code></a> and <a href="http://de2.php.net/manual/en/function.is-null.php" rel="noreferrer"><code>is_null()</code></a> for that. It will return <code>TRUE</code> if the key exists and has a value far from <code>NULL</code>

Difference:

<pre><code>$arr = array('a' =&gt; NULL);

var_dump(array_key_exists('a', $arr)); // --&gt; TRUE
var_dump(isset($arr['a'])); // --&gt; FALSE
</code></pre>

So you should check:

<pre><code>if(array_key_exists($key, $array) &amp;&amp; is_null($array[$key])) {
 echo "key exists with a value of NULL";
}
</code></pre>

blocks|key|104026|text|foreach($array+as+$i+=>+$v)+{
++++if(null+===+$v)+{
++++++++//+this+item+($array[$i])+is+null
++++}
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|104027|...or，对于给定的键：|unstyled|104028|if(null+===+$array[2])+{
+++++//+this+item+($array[2])+is+null
}|104029|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|L|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|I|3|-4|5|F|7|N|8|@]|9|@]|A|$]]]|J|$]]

<pre><code>foreach($array as $i =&gt; $v) {
 if(null === $v) {
 // this item ($array[$i]) is null
 }
}
</code></pre>

...or, for a given key:

<pre><code>if(null === $array[2]) {
 // this item ($array[2]) is null
}
</code></pre>

blocks|key|104044|text|if+(+!isset($array[$key])+%7C%7C+$array[$key]+==+""+%7C%7C+is_null($array[$key])+)
{
++++//given+key+does+not+exist+or+it+has+""+or+NULL+value
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|104045|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>if ( !isset($array[$key]) || $array[$key] == "" || is_null($array[$key]) )
{
 //given key does not exist or it has "" or NULL value
}
</code></pre>

blocks|key|104085|text|如果我知道数组是如何构造的，这可能会更清楚，但是，假设您在数组中既可以有空字符串，也可以有null值，并且您想要说明0的值-->下面是我要做的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|104086|if+(is_null($array[$key])+%7C%7C+(string)$array[$key]+==+'')|code-block|syntax|javascript|104087|下面是一小段测试代码，用一个同时包含0、null、空字符串和非零整数的数组展示了它的作用……|104088|$array+=+array(0,1,null,2,'');
print_r($array);

foreach+($array+as+$key+=>+$val)+{
+++++++++if+(is_null($array[$key])+%7C%7C+(string)$array[$key]+==+'')+{
+++++++++++echo+$key.",+true\n";
+++++++++}
}|104089|至于使用isset()+--认为设置了一个空字符串。这可能是你遇到的情况(除了0被认为是空的)与下面的用法相比：|104090|$foo+=+array(0,1,null,2,'');

print_r($foo);
foreach+($foo+as+$key+=>+$val)+{
++++++++if+(isset($foo[$key]))+{
++++++++++++++++echo+$key.",+true\n";
++++++++}
}|104091|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

Potentially this could be cleaner if I knew how the array was constructed, but, having the assumption that you can have both empty strings, or nulls in the array, and you want to account for values of 0 --> here's what I'd do:

<pre><code>if (is_null($array[$key]) || (string)$array[$key] == '')
</code></pre>

Here's a little bit of test code showing it in action with an array that has both 0, null, an empty string, and non-zero integers...

<pre><code>$array = array(0,1,null,2,'');
print_r($array);

foreach ($array as $key =&gt; $val) {
 if (is_null($array[$key]) || (string)$array[$key] == '') {
 echo $key.", true\n";
 }
}
</code></pre>

As for using isset() -- an empty string is consider to be set. Which may be what you're running into (aside from 0 being considered empty) Compare with this usage:

<pre><code>$foo = array(0,1,null,2,'');

print_r($foo);
foreach ($foo as $key =&gt; $val) {
 if (isset($foo[$key])) {
 echo $key.", true\n";
 }
}
</code></pre>

blocks|key|321021|text|我看了所有的答案，但我不喜欢。这不是更简单更好吗？这就是我正在使用的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|321022|++if+(in_array(null,+$array,+true)+%7C%7C+in_array('',+$array,+true))+{
++++//+There+are+null+(or+empty)+values.
++}|code-block|syntax|javascript|321023|请注意，将第三个参数设置为true意味着严格比较，这意味着0不等于null+-然而，空字符串('')也不等于-这就是为什么我们有两个条件。不幸的是，in_array中的第一个参数必须是字符串，而不能是值数组。|321024|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Looked at all the answers and I don't like them. Isn't this much simpler and better? It's what I am using:

<pre><code> if (in_array(null, $array, true) || in_array('', $array, true)) {
 // There are null (or empty) values.
 }
</code></pre>

Note that setting the third parameter as true means strict comparison, this means 0 will not equal null - however, neither will empty strings ('') - this is why we have two conditions. Unfortunately the first parameter in in_array has to be a string and cannot be an array of values.

In the following associative array 

<pre><code>$array = array(
 [0] =&gt; 0
 [1] =&gt; 1
 [2] =&gt; 
 [3] =&gt; 2
 [4] =&gt; 
)
</code></pre>

how can you determine if a given key has an empty (or null) value? I used 

<pre><code>if(empty($array[$value])) 
</code></pre>

and 

<pre><code>if(isset($array[$value])) &amp;&amp; $array[$value] !=='')
</code></pre>

When using <code>empty</code> I also get <code>false</code> for the first array value which is zero and <code>isset</code> doesn't seem to do the trick.

How to check if an associative array has an empty or null value

在下面的关联数组中$array = array(    [0] => 0    [1] => 1    [2] =>     [3] => 2    [4] => )如何确定给定的键是否具有空(或null)值？我用过if(empty($array[$value])) 和if(isset($array[$value]))...

问如何检查关联数组是否为空或null值
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