blocks|key|1523652|text|array_keys返回一个键数组。取第一个条目。或者，您可以在数组上调用reset，然后调用key。后一种方法可能会稍微快一点(尽管我没有测试它)，但它有重置内部指针的副作用。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1523653|entityMap^0|0|A|11|5|1B|3|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|O|8|@]|D|@]|E|$]]]|G|$]]

<code>array_keys</code> returns an array of keys. Take the first entry. Alternatively, you could call <code>reset</code> on the array, and subsequently <code>key</code>. The latter approach is probably slightly faster (Thoug I didn't test it), but it has the side effect of resetting the internal pointer.

blocks|key|1308614|text|key($an_array)会给你第一个密钥|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1308615|edit+per+Blixt:您应该在key($an_array)之前调用reset($array);以将指针重置到数组的开头。|1308616|entityMap^0|0|E|0|J|E|11|E|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|R|8|@]|D|@]|E|$]]]|I|$]]

<code>key($an_array)</code> will give you the first key

edit per Blixt: you should call <code>reset($array);</code> before <code>key($an_array)</code> to reset the pointer to the beginning of the array.

blocks|key|1523743|text|你可以试一试|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1523744|array_keys($data)[0]|code-block|syntax|javascript|1523745|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

You could try

<pre><code>array_keys($data)[0]
</code></pre>

blocks|key|1523701|text|list($firstKey)+=+array_keys($yourArray);|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1523702|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>list($firstKey) = array_keys($yourArray);
</code></pre>

blocks|key|1523692|text|请查找以下内容：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1523693|$yourArray+=+array('first_key'=>+'First',+2,+3,+4,+5);
$keys+++=+++array_keys($yourArray);
echo+"Key+=+".$keys[0];|code-block|syntax|javascript|1523694|Working+Example:|offset|length|1523695|entityMap|0|LINK|mutability|MUTABLE|url|https://3v4l.org/c88jk^0|0|0|0|G|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

Please find the following:

<pre><code>$yourArray = array('first_key'=&gt; 'First', 2, 3, 4, 5);
$keys = array_keys($yourArray);
echo "Key = ".$keys[0];
</code></pre>

<a href="https://3v4l.org/c88jk" rel="nofollow noreferrer">Working Example:</a>

blocks|key|1523704|text|$myArray+=+array(
++++2+=>+'3th+element',
++++4+=>+'first+element',
++++1+=>+'second+element',
++++3+=>+'4th+element'
);
echo+min(array_keys($myArray));+//+return+1|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1523705|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>$myArray = array(
 2 =&gt; '3th element',
 4 =&gt; 'first element',
 1 =&gt; 'second element',
 3 =&gt; '4th element'
);
echo min(array_keys($myArray)); // return 1
</code></pre>

blocks|key|1523732|text|这也可以是一种解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1523733|$yourArray+=+array('first_key'=>+'First',+2,+3,+4,+5);
$first_key+=+current(array_flip($yourArray));
echo+$first_key;|code-block|syntax|javascript|1523734|我已经测试过了，它工作正常。|1523735|Working+Code。|offset|length|1523736|entityMap|0|LINK|mutability|MUTABLE|url|https://3v4l.org/1HPm4^0|0|0|0|0|C|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|X|8|@]|9|@$K|Y|L|Z|1|10]]|A|$]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

This could also be a solution:

<pre><code>$yourArray = array('first_key'=&gt; 'First', 2, 3, 4, 5);
$first_key = current(array_flip($yourArray));
echo $first_key;
</code></pre>

I have tested it and it works.

<a href="https://3v4l.org/1HPm4" rel="nofollow noreferrer">Working Code</a>.

blocks|key|1308990|text|为了增强Webmut的解决方案，我添加了以下解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1308991|$firstKey+=+array_keys(array_slice($array,+0,+1,+TRUE))[0];|code-block|syntax|javascript|1308992|我在PHP7.1上的输出是：|1308993|foreach+to+get+first+key+and+value:+0.048566102981567+seconds+
reset%2Bkey+to+get+first+key+and+value:+0.11727809906006+seconds+
reset%2Bkey+to+get+first+key:+0.11707186698914+seconds+
array_keys+to+get+first+key:+0.53917098045349+seconds+
array_slice+to+get+first+key:+0.2494580745697+seconds+|1308994|如果我对一个大小为10000的数组执行此操作，则结果为|1308995|foreach+to+get+first+key+and+value:+0.048488140106201+seconds+
reset%2Bkey+to+get+first+key+and+value:+0.12659382820129+seconds+
reset%2Bkey+to+get+first+key:+0.12248802185059+seconds+
array_slice+to+get+first+key:+0.25442600250244+seconds+|1308996|array_keys方法的超时时间为30秒(对于1000个元素，其余元素的时间大致相同，但array_keys方法的超时时间约为7.5秒)。|1308997|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/21219594/8601807^0|4|6|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@$A|11|B|12|1|13]]|C|$]]|$1|D|3|E|5|F|7|14|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|15|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|16|8|@]|9|@]|C|$G|H]]|$1|M|3|N|5|6|7|17|8|@]|9|@]|C|$]]|$1|O|3|P|5|F|7|18|8|@]|9|@]|C|$G|H]]|$1|Q|3|R|5|6|7|19|8|@]|9|@]|C|$]]|$1|S|3|-4|5|6|7|1A|8|@]|9|@]|C|$]]]|T|$U|$5|V|W|X|C|$Y|Z]]]]

To enhance on the solution of <a href="https://stackoverflow.com/a/21219594/8601807">Webmut</a>, I've added the following solution:

<pre><code>$firstKey = array_keys(array_slice($array, 0, 1, TRUE))[0];
</code></pre>

The output for me on PHP 7.1 is:

<pre><code>foreach to get first key and value: 0.048566102981567 seconds 
reset+key to get first key and value: 0.11727809906006 seconds 
reset+key to get first key: 0.11707186698914 seconds 
array_keys to get first key: 0.53917098045349 seconds 
array_slice to get first key: 0.2494580745697 seconds 
</code></pre>

If I do this for an array of size 10000, then the results become

<pre><code>foreach to get first key and value: 0.048488140106201 seconds 
reset+key to get first key and value: 0.12659382820129 seconds 
reset+key to get first key: 0.12248802185059 seconds 
array_slice to get first key: 0.25442600250244 seconds 
</code></pre>

The array_keys method times out at 30 seconds (with only 1000 elements, the timing for the rest was about the same, but the array_keys method had about 7.5 seconds).

blocks|key|1308686|text|+$arr+=+array('key1'=>'value1','key2'=>'value2','key3'=>'key3');
+list($first_key)+=+each($arr);
+print+$first_key;
+//+key1|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1308687|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> $arr = array('key1'=&gt;'value1','key2'=&gt;'value2','key3'=&gt;'key3');
 list($first_key) = each($arr);
 print $first_key;
 // key1
</code></pre>

blocks|key|1308867|text|这是我找到的最简单的方法。快速且只有两行代码:-D|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1308868|$keys+=+array_keys($array);
echo+$array[$keys[0]];|code-block|syntax|javascript|1308869|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This is the easier way I had ever found. Fast and only two lines of code :-D

<pre><code>$keys = array_keys($array);
echo $array[$keys[0]];
</code></pre>

blocks|key|1308787|text|对我来说最好的办法就是|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1308788|array_shift(array_keys($array))|code-block|syntax|javascript|1308789|array_keys从初始数组中获取键的数组，然后array_shift从它的第一个元素值中剪切。为此，您需要使用PHP+5.4%2B。|offset|length|style|CODE|1308790|entityMap^0|0|0|0|A|P|B|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]|$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|N|$]]

The best way that worked for me was 

<pre><code>array_shift(array_keys($array))
</code></pre>

<code>array_keys</code> gets array of keys from initial array and then <code>array_shift</code> cuts from it first element value.
You will need PHP 5.4+ for this.

blocks|key|1524074|text|php73：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1524075|$array+=+['a'+=>+'..',+'b'+=>+'..'];

array_key_first($array);+//+'a'
array_key_last($array);+//+'b';|code-block|syntax|javascript|1524076|http://php.net/manual/en/function.array-key-first.php|offset|length|1524077|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|0|1H|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|S|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|T|8|@]|9|@$I|U|J|V|1|W]]|A|$]]|$1|K|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|H]]]]

php73:

<pre><code>$array = ['a' =&gt; '..', 'b' =&gt; '..'];

array_key_first($array); // 'a'
array_key_last($array); // 'b';
</code></pre>

<a href="http://php.net/manual/en/function.array-key-first.php" rel="nofollow noreferrer">http://php.net/manual/en/function.array-key-first.php</a>

blocks|key|1524171|text|由于PHP7.3.0函数可以使用array_key_first()。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1524172|有几种方法可以为PHP+7.3.0之前的版本提供此功能。可以使用array_keys()，但效率可能会很低。也可以使用reset()和key()，但这可能会更改内部数组指针。一个有效的解决方案，它不会改变内部数组指针，写成polyfill：|1524173|<?php
if+(!function_exists('array_key_first'))+{
++++function+array_key_first(array+$arr)+{
++++++++foreach($arr+as+$key+=>+$unused)+{
++++++++++++return+$key;
++++++++}

++++++++return+null;
++++}
}
?>|code-block|syntax|javascript|1524174|entityMap|0|LINK|mutability|MUTABLE|url|https://www.php.net/manual/en/function.array-key-first.php^0|G|H|G|H|0|0|W|C|1N|7|1V|5|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@$9|X|A|Y|1|Z]]|E|$]]|$1|F|3|G|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|17|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|18|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

Since PHP 7.3.0 function <a href="https://www.php.net/manual/en/function.array-key-first.php" rel="nofollow noreferrer"><code>array_key_first()</code></a> can be used.
There are several ways to provide this functionality for versions prior to PHP 7.3.0. It is possible to use <code>array_keys()</code>, but that may be rather inefficient. It is also possible to use <code>reset()</code> and <code>key()</code>, but that may change the internal array pointer. An efficient solution, which does not change the internal array pointer, written as polyfill:
<pre><code>&lt;?php
if (!function_exists('array_key_first')) {
 function array_key_first(array $arr) {
 foreach($arr as $key =&gt; $unused) {
 return $key;
 }

 return null;
 }
}
?&gt;
</code></pre>

blocks|key|1524214|text|这是@Blixt的答案，在7.3.0之前，可以使用这个polyfill：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1524215|if+(!function_exists('array_key_first'))+{
++function+array_key_first(array+$array)+{
++++return+key(array_slice($array,+0,+1,+true));
++}
}|code-block|syntax|javascript|1524216|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Re the @Blixt answer, prior to 7.3.0, this polyfill can be used:
<pre><code>if (!function_exists('array_key_first')) {
 function array_key_first(array $array) {
 return key(array_slice($array, 0, 1, true));
 }
}
</code></pre>

blocks|key|1309193|text|这将适用于所有PHP版本|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1309194|$firstKey+=+''+;

//$contact7formlist+-+associative+array.+

if(function_exists('array_key_first')){
++++
++++$firstKey+=+array_key_first($contact7formlist);
++++
}else{
++++
++++foreach+($contact7formlist+as+$key+=>+$contact7form+){
++++++++$firstKey+=+$key;
++++++++break;
++++}
}|code-block|syntax|javascript|1309195|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This will work on all PHP versions
<pre><code>$firstKey = '' ;

//$contact7formlist - associative array. 

if(function_exists('array_key_first')){
 
 $firstKey = array_key_first($contact7formlist);
 
}else{
 
 foreach ($contact7formlist as $key =&gt; $contact7form ){
 $firstKey = $key;
 break;
 }
}
</code></pre>

blocks|key|1308726|text|一句话：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1308727|$array+=+array('key1'=>'value1','key2'=>'value2','key3'=>'key3');
echo+key(+array_slice(+$array,+0,+1,+true+)+);

#+echos+'key1'|code-block|syntax|javascript|1308728|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

A one-liner:

<pre><code>$array = array('key1'=&gt;'value1','key2'=&gt;'value2','key3'=&gt;'key3');
echo key( array_slice( $array, 0, 1, true ) );

# echos 'key1'
</code></pre>

blocks|key|1308929|text|今天，我必须搜索由POST请求返回的数组的第一个键。(并记下表单id的编号等)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1308930|好吧，我找到了这个：Return+first+key+of+associative+array+in+PHP|offset|length|1308931|http://php.net/key|1308932|我已经这样做了，并且它起作用了。|1308933|++++$data+=+$request->request->all();
++++dump($data);
++++while+($test+=+current($data))+{
++++++++dump($test);
++++++++echo+key($data).'<br+/>';die();
++++++++break;
++++}|code-block|syntax|javascript|1308934|也许它会和另一个人在一起15分钟。CYA。|1308935|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/6698428/return-first-key-of-associative-array-in-php|1^0|0|A|18|0|0|0|I|1|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Z|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|10|8|@]|9|@$D|11|E|12|1|13]]|A|$]]|$1|F|3|G|5|6|7|14|8|@]|9|@$D|15|E|16|1|17]]|A|$]]|$1|H|3|I|5|6|7|18|8|@]|9|@]|A|$]]|$1|J|3|K|5|L|7|19|8|@]|9|@]|A|$M|N]]|$1|O|3|P|5|6|7|1A|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|1B|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|X]]|Y|$5|T|U|V|A|$W|G]]]]

Today I had to search for the first key of my array returned by a POST request. (And note the number for a form id etc)

Well, I've found this:
<a href="https://stackoverflow.com/questions/6698428/return-first-key-of-associative-array-in-php">Return first key of associative array in PHP</a>

<a href="http://php.net/key" rel="nofollow noreferrer">http://php.net/key</a>

I've done this, and it work.

<pre><code> $data = $request-&gt;request-&gt;all();
 dump($data);
 while ($test = current($data)) {
 dump($test);
 echo key($data).'&lt;br /&gt;';die();
 break;
 }
</code></pre>

Maybe it will eco 15min of an other guy.
CYA.

blocks|key|1309072|text|我认为最好也是最快的方法是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1309073|$first_key=key(array_slice($array,+0,+1,+TRUE))|code-block|syntax|javascript|1309074|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I think the best and fastest way to do it is:
<pre><code>$first_key=key(array_slice($array, 0, 1, TRUE))
</code></pre>

blocks|key|1309223|text|array_chunk将数组拆分为块，您可以使用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1309224|$arr+=+['uno'=>'one','due'=>'two','tre'=>'three'];
$firstElement+=+array_chunk($arr,1,true)[0];
var_dump($firstElement);|code-block|syntax|javascript|1309225|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

array_chunk split an array into chunks, you can use:
<pre><code>$arr = ['uno'=&gt;'one','due'=&gt;'two','tre'=&gt;'three'];
$firstElement = array_chunk($arr,1,true)[0];
var_dump($firstElement);
</code></pre>

blocks|key|1524093|text|使用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1524094|$array+=+['po','co','so'];

echo+reset($array);+|code-block|syntax|javascript|1524095|结果:+po|1524096|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|$]]

use :
<pre><code>$array = ['po','co','so'];

echo reset($array); 
</code></pre>
Result : po

What's the best way to determine the first key in a possibly associative array? My first thought it to just foreach the array and then immediately breaking it, like this:

<pre><code>foreach ($an_array as $key =&gt; $val) break;
</code></pre>

Thus having $key contain the first key, but this seems inefficient. Does anyone have a better solution?

Get first key in a (possibly) associative array?

确定可能的关联数组中的第一个键的最佳方法是什么？我的第一个想法是先对数组进行预取，然后立即对其进行分解，如下所示：foreach ($an_array as $key => $val) break;因此，让$key包含第一个密钥，但这似乎效率很低。有人有更好的解决方案吗？

问获取(可能)关联数组中的第一个键？
EN

回答 20

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