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array_combine

(PHP 5, PHP 7)

array_combine — 创建一个数组，用一个数组的值作为其键名，另一个数组的值作为其值

说明

array array_combine ( array $keys , array $values )

返回一个 array ，用来自 keys 数组的值作为键名，来自 values 数组的值作为相应的值。

参数

keys: 将被作为新数组的键。非法的值将会被转换为字符串类型（ string ）。
values: 将被作为数组的值。

返回值

返回合并的 array ，如果两个数组的单元数不同则返回 FALSE 。

错误／异常

如果作为keys的数组和作为values的数组的元素个数不一样，将会抛出一个警告错误（ E_WARNING ）。

更新日志

版本	说明
5.4.0	（修复）早期版本中如果是空数组就报 `E_WARNING` 的错并且返回 `FALSE` 。

范例

Example #1 一个 array_combine() 简单的例子

  <?php
$a  = array( 'green' ,  'red' ,  'yellow' );
 $b  = array( 'avocado' ,  'apple' ,  'banana' );
 $c  =  array_combine ( $a ,  $b );

 print_r ( $c );
 ?>

以上例程会输出：

Array
(
    [green]  => avocado
    [red]    => apple
    [yellow] => banana
)

参见

array_merge() - 合并一个或多个数组
array_walk() - 使用用户自定义函数对数组中的每个元素做回调处理
array_values() - 返回数组中所有的值

用户评论:

[#1] welcome at el hyphen mustafa [2015-11-29 21:46:30]

Further to loreiorg's script
in order to preserve duplicate keys when combining arrays.

I have modified the script to use a closure instead of create_function

Reason: see security issue flagged up in the documentation concerning create_function

<?php function array_combine_($keys, $values){ $result = array(); foreach ($keys as $i => $k) { $result[$k][] = $values[$i]; } array_walk($result, function(&$v){ $v = (count($v) == 1) ? array_pop($v): $v; }); return $result; } ?>

[#2] info at maisuma dot jp [2015-03-04 01:00:46]

array_combine() returns NULL instrad of FALSE, when non-array parameters are given (issuing warning).

<?php //NULL var_dump(array_combine('string',array(42))); ?>

[#3] ilanfir at gmail dot com [2015-02-15 10:58:59]

I recently had to flip an array and group the elements by value, this snippet will do that:
<?php function flipAndGroup($input) {     $outArr = array();     array_walk($input, function($value, $key) use (&$outArr) {         if(!isset($outArr[$value]) || !is_array($outArr[$value])) {             $outArr[$value] = [];         }         $outArr[$value][] = $key;     });     return $outArr; } ?>

Example:
<?php $users_countries = array(     'username1' => 'US',     'user2' => 'US',     'newuser' => 'GB' ); print_r(flipAndGroup($users_countries)); ?>

Returns:
Array
(
    [US] => Array
        (
            [0] => username1
            [1] => user2
        )

    [GB] => Array
        (
            [0] => newuser
        )
)

[#4] ismorodin at hotmail dot com [2014-06-04 15:48:38]

Function eliminates the error Throws E_WARNING if the number of elements in keys and values ??does not match.

function arrCombine($arr1 = array(),$arr2 = array()){
if(is_array($arr1) && is_array($arr2)):
$cntArr1 = count($arr1);
$cntArr2 = count($arr2);
$difference = max($cntArr1,$cntArr2) - min($cntArr1,$cntArr2);
if($cntArr1 > $cntArr2):
for ($i=1;$i<=$difference;$i++){
$arr2[$cntArr2+$i] = $cntArr2 + 1;
}
return array_combine($arr1,$arr2);
elseif($cntArr1 < $cntArr2):
for ($i=1;$i<=$difference;$i++){
$arr1[$cntArr1+$i] = count($arr1) + 1;
}
return array_combine($arr1,$arr2);
else:
return array_combine($arr1,$arr2);
endif;
endif;
}
$array = [1,4,5,6,7,8];
$array2 = ['john','smith'];

var_dump( arrCombine($array,$array2 ));

array (size=6)
  1 => string 'john' (length=4)
  4 => string 'smith' (length=5)
  5 => int 3
  6 => int 3
  7 => int 3
  8 => int 3

var_dump( arrCombine($array2,$array) );

array (size=6)
  'john' => int 1
  'smith' => int 4
  3 => int 5
  4 => int 6
  5 => int 7
  6 => int 8

[#5] loureirorg at gmail dot com [2013-03-14 10:48:00]

If two keys are the same, the second one prevails.

Example:
<?php print_r(array_combine(Array('a','a','b'), Array(1,2,3))); ?>
Returns:
Array
(
    [a] => 2
    [b] => 3
)

But if you need to keep all values, you can use the function below:

<?php function array_combine_($keys, $values) {     $result = array();     foreach ($keys as $i => $k) {         $result[$k][] = $values[$i];     }     array_walk($result, create_function('&$v', '$v = (count($v) == 1)? array_pop($v): $v;'));     return    $result; } print_r(array_combine_(Array('a','a','b'), Array(1,2,3))); ?>
Returns:
Array
(
    [a] => Array
        (
            [0] => 1
            [1] => 2
        )

    [b] => 3
)

[#6] aaron at aaronholmes dot net [2013-01-22 16:54:02]

You can create an array hashset from a flat array, storing both keys and values, with array_combine(). This works with duplicate values in the array too.

<?php $flat_array = array(         'one',         'two',         'three',         'three',         'four',         'one' ); $set = array_combine($flat_array, $flat_array); var_dump($set); ?>

This outputs the following:

array(4) {
    ["one"]=>
        string(3) "one"
    ["two"]=>
        string(3) "two"
    ["three"]=>
        string(5) "three"
    ["four"]=>
        string(4) "four"
}

[#7] g.REMOVETHIS.vincendon AT vithemis.com [2012-07-18 09:41:12]

I was looking for a function that could combine an array to multiple one, for my MySQL GROUP_CONCAT() query, so I made this function.

<?php function array_combine_array(array $keys) { $arrays = func_get_args(); $keys = array_shift($arrays); $check = count(array_unique(array_map('is_array',array_map('current',$arrays)))) === 1; if (!$check) { trigger_error('Function array_combine_array() expects all parameters to be same type array or array of array',E_USER_NOTICE); return array(); } $assocArray = is_array(array_shift(array_map('current',$arrays))); if (empty($keys)) $keys = array_keys(array_fill(0,max(($assocArray) ? array_map('count',array_map('current',$arrays)) : array_map('count',$arrays)),'foo')); $ret=array();$i=0; foreach($keys as $v) { foreach ($arrays as $k) { if ($assocArray) { $key = key($k); $ret[$v][$key] = isset($k[$key][$i]) ? $k[$key][$i]:false; } else $ret[$v][] = isset($k[$i]) ? $k[$i]: false; } $i++; } return $ret; } $r = array(1,2,4,10); $a1 = array('one','two','four','ten'); $a2 = array('un','deux','quatre','dix'); $a3 = array('uno','dos','quatro','diez'); print_r(array_combine_array($r,array('english' => $a1),array('french' => $a2),array('spanish' => $a3))); print_r(array_combine_array($r,$a1,array('french' => $a2),array('spanish' => $a3))); print_r(array_combine_array($r,$a1,$a2,$a3)); print_r(array_combine_array(array(),array('english' => $a1),array('french' => $a2),array('spanish' => $a3))); ?>

[#8] dejiakala at gmail dot com [2011-10-27 03:32:50]

I needed to read CSV files into associative arrays with column headers as keys. Then I ran into a problem when you have empty columns at the end of a row because array_combine returns false if both arrays don't have the same number of elements. This function based on quecoder at gmail's combine_arr() below allowed me to pad either array or not when parsing my CSVs to arrays.
$a is the array of header columns and $b is an array of the current row retrieved with fgetcsv()

<?php function array_combine_special($a, $b, $pad = TRUE) { $acount = count($a); $bcount = count($b); // more elements in $a than $b but we don't want to pad either if (!$pad) { $size = ($acount > $bcount) ? $bcount : $acount; $a = array_slice($a, 0, $size); $b = array_slice($b, 0, $size); } else { // more headers than row fields if ($acount > $bcount) { $more = $acount - $bcount; // how many fields are we missing at the end of the second array? // Add empty strings to ensure arrays $a and $b have same number of elements $more = $acount - $bcount; for($i = 0; $i < $more; $i++) { $b[] = ""; } // more fields than headers } else if ($acount < $bcount) { $more = $bcount - $acount; // fewer elements in the first array, add extra keys for($i = 0; $i < $more; $i++) { $key = 'extra_field_0' . $i; $a[] = $key; } } } return array_combine($a, $b); } ?>

[#9] Dan LaManna [2011-09-17 20:12:05]

I needed a function that truncated extra values, and only went as far as keys without throwing a warning as array_combine does.

<?php function safeArrayCombine($keys, $values) { $combinedArray = array(); for ($i=0, $keyCount = count($keys); $i < $keyCount; $i++) { $combinedArray[$keys[$i]] = $values[$i]; } return $combinedArray; } ?>

[#10] zequez at gmail dot com [2011-03-27 15:51:35]

If two keys are the same, the second one prevails.
Example:
<?php print_r(array_combine(Array('a','a','b'), Array(1,2,3))); ?>
Returns:
Array
(
[a] => 2
[b] => 3
)

[#11] claude dot pache at gmail dot com [2010-05-12 10:04:51]

array_combine() has a strange bug/misfeature (as of PHP 5.3.2): There is no logical reason for <?php array_combine(array(), array()) ?#=#> throwing a warning and returning FALSE, instead of returning <?php array() ?> (see http://bugs.php.net/bug.php?id=34857). Here is a quick workaround:
<?php function array_real_combine($a, $b) { return $a===array() && $b===array() ? array() : array_combine($a, $b); } ?>

[#12] bradentkeith at dot dontspam dot gmail dot com [2010-04-01 12:20:01]

I needed a function that would take keys from one unequal array and combine them with the values of another. Real life application:
Select 4 product types.
Each product has a serial.
There are 4 sets of products.

<?php         function array_combine2($arr1, $arr2) {             $count1 = count($arr1);             $count2 = count($arr2);             $numofloops = $count2/$count1;                              $i = 0;             while($i < $numofloops){                 $arr3 = array_slice($arr2, $count1*$i, $count1);                 $arr4[] = array_combine($arr1,$arr3);                 $i++;             }                          return $arr4;         }     ?>

Input:
Array
(
    [0] => SMART Board
    [1] => Projector
    [2] => Speakers
    [3] => Splitter
)
, Array
(
    [0] => serial to smart board1
    [1] => serial to projector 1
    [2] => serial to speakers 1
    [3] => serials to splitter 1
    [4] => serials to smart board 2
    [5] => serials to projector 2
    [6] => serials to speakers 2
    [7] => serials to splitter 2
)

Array
(
    [0] => Array
        (
            [SMART Board] => serial to smart board1
            [Projector] => serial to projector 1
            [Speakers] => serial to speakers 1
            [Splitter] => serials to splitter 1
        )

    [1] => Array
        (
            [SMART Board] => serials to smart board 2
            [Projector] => serials to projector 2
            [Speakers] => serials to speakers 2
            [Splitter] => serials to splitter 2
        )

)

[#13] xavier at api-meal dot eu [2009-09-23 03:37:58]

<?php function array_alternatives(array $first_element, array $second_element) { $lists = func_get_args(); $total_lists = func_num_args(); for($i=0; $i<$total_lists; $i++) { $list =& $lists[$i]; if (is_array($list) === FALSE) throw new Exception("Parameter $i is not an array."); if (count($list) === 0) throw new Exception("Parameter $i has no element."); unset($list); } // Initialize our alternatives $alternatives = array(); foreach($lists[0] as &$value) { array_push($alternatives, array($value)); unset($value); } unset($lists[0]); // Process alternatives for($i=1; $i<$total_lists; $i++) { $list =& $lists[$i]; $new_alternatives = array(); foreach($list as &$value) { foreach($alternatives as $_) { array_push($_, $value); array_push($new_alternatives, $_); } } // Rotate references, it's cheaper than copy array like `$alternatives = $new_alternatives;` $alternatives =& $new_alternatives; unset($new_alternatives, $list, $lists[$i]); } return $alternatives; } ?>

[#14] quecoder at gmail [2008-08-26 00:00:56]

<?php // If they are not of same size, here is solution: $abbreviations = array("AL", "AK", "AZ", "AR", "TX", "CA"); $states = array("Alabama", "Alaska", "Arizona", "Arkansas"); function combine_arr($a, $b) { $acount = count($a); $bcount = count($b); $size = ($acount > $bcount) ? $bcount : $acount; $a = array_slice($a, 0, $size); $b = array_slice($b, 0, $size); return array_combine($a, $b); } $combined = combine_arr($abbreviations, $states); print_r($combined); // Output // Array ( [AL] => Alabama [AK] => Alaska [AZ] => Arizona // [AR] => Arkansas ) ?>

[#15] J.D.D. [2008-08-09 13:31:29]

This may be obvious, but I don't see anything about it on the manual page, so a friendly warning...  The array you are using as keys must have all unique values.  If not, array elements get dropped.

<?php $arr_notUnique = array('one' , 'one' , 'two'); $arr_b = array('red' , 'green' , 'blue'); $arr_combo = array_combine($arr_notUnique, $arr_b); ?>

Results:  Array ( [one] => green [two] => blue )

NOT:  Array ( [one] => red [one] => green [two] => blue )

[#16] Mike Jean [2008-03-18 21:59:04]

Khaly's PHP4 code below does not work correctly in all cases. Consider when your array consists of floats:

<?php $okay = array(0, 10, 20, 30); $not_okay = array(0, 0.5, 1, 1.5); $foo = array_combine($okay, $okay); $bar = array_combine($not_okay, $not_okay); ?>

What can you do? In my case, I was just zipping up some select-box options, so I converted everything in my floats to strings.

[#17] Khaly [2007-10-04 02:11:48]

This is the function for PHP4 :

<?php function array_combine($arr1,$arr2) { $out = array(); foreach($arr1 as $key1 => $value1) { $out[$value1] = $arr2[$key1]; } return $out } ?>

[#18] neoyahuu at yahoo dot com [2007-03-19 20:36:24]

Some tips for merging same values in an array

<?php $array1 = array(1,2,3,4,5,6,7,8,9,10,11,12); $array2 = array(1,2,3,13); $merged = array_merge($array1,$array2); // output normal array_merge echo '<pre>After array_merge : '; print_r($merged); echo '</pre>'; // do double flip for merging values in an array $merged = array_flip($merged); $merged = array_flip($merged); // Output after echo '<pre>After Double Flip : '; print_r($merged); echo '</pre>'; ?>

Output ::

After array_merge :
Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5
    [5] => 6
    [6] => 7
    [7] => 8
    [8] => 9
    [9] => 10
    [10] => 11
    [11] => 12
    [12] => 1
    [13] => 2
    [14] => 3
    [15] => 13
)

After Double Flip :
Array
(
    [12] => 1
    [13] => 2
    [14] => 3
    [3] => 4
    [4] => 5
    [5] => 6
    [6] => 7
    [7] => 8
    [8] => 9
    [9] => 10
    [10] => 11
    [11] => 12
    [15] => 13
)