数组 函数
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array_combine

(PHP 5)

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。

如果两个数组的单元数不同或者数组为空时返回 FALSE。

Example #1 简单的 array_combine() 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()，array_walk() 和 array_values()。

参数

keys

Array of keys to be used. Illegal values for key will be converted to string.

values

Array of values to be used

返回值

Returns the combined array, FALSE if the number of elements for each array isn't equal.

错误/异常

Throws E_WARNING if the number of elements in keys and values does not match.

更新日志

版本 说明
5.4.0 Previous versions issued E_WARNING and returned FALSE for empty arrays.

范例

Example #2 A simple array_combine() example

<?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

数组 函数
在线手册：中文 英文
PHP手册
PHP手册 - N: 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

用户评论:

dejiakala at gmail dot com (27-Oct-2011 11:32)

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);
}
?>

Dan LaManna (18-Sep-2011 04:12)

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;
}
?>

zequez at gmail dot com (27-Mar-2011 11:51)

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
)

claude dot pache at gmail dot com (12-May-2010 06:04)

array_combine() has a strange bug/misfeature (as of PHP 5.3.2): There is no logical reason for <? array_combine(array(), array()) ?> throwing a warning and returning FALSE, instead of returning <? 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);
}
?>

bradentkeith at dot dontspam dot gmail dot com (01-Apr-2010 08:20)

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
        )

)

xavier at api-meal dot eu (23-Sep-2009 11:37)

<?php
/**
 * Return alternatives defined by values of each parameters.
 *
 * Exemple :
 *
 * array_alternatives(array('foo','bar'), array('baz', 'qux'));
 * array(
 *     array('foo', 'baz'),
 *     array('bar', 'baz'),
 *     array('foo', 'qux'),
 *     array('bar', 'qux'),
 * );
 *
 * array_alternatives(array('a'), array('simple-minded'), array('solution'));
 * array(
 *     array('a', 'simple-minded', 'solution')
 * );
 *
 * array_alternatives(array('a'), array('red', 'blue'), array('car'));
 * array(
 *     array('a', 'red',  'car'),
 *     array('a', 'blue', 'car'),
 * );
 * 
 * @param array $first_element
 * @param array $second_element
 * @return array
 * @author Xavier Barbosa
 */
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;
}
?>

quecoder at gmail (26-Aug-2008 08:00)

<?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 )
?>

J.D.D. (09-Aug-2008 09:31)

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 )

Zoran (02-Apr-2008 12:57)

Also, Khalys function only works if keys of both arrays are the same because array_combine ignores keys. An easy way to ignore them is by taking array_values(). Floats can be casted to strings to avoid overwriting.

So, the PHP4 function could look something like this:
<?php
function array_combine($arr1, $arr2) {
    $out = array();
   
    $arr1 = array_values($arr1);
    $arr2 = array_values($arr2);
   
    foreach($arr1 as $key1 => $value1) {
        $out[(string)$value1] = $arr2[$key1];
    }
   
    return $out;
}
?>

Mike Jean (19-Mar-2008 05:59)

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);

/*

Results:

$foo = {
  [0]=> int(0)
  [10]=> int(10)
  [20]=> int(20)
  [30]=> int(30)
}

$bar = {
  [0]=> float(0.5)
  [1]=> float(1.5)
}

*/

?>

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.

Khaly (04-Oct-2007 10:11)

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
}

?>

neoyahuu at yahoo dot com (20-Mar-2007 04:36)

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
)

ifeghali at interveritas dot net (26-Feb-2005 06:53)

Use that code to group an array by its first element.

<?

function groupbyfirst($array)
{
    foreach ($array as $row)
    {
        $firstkey = array_keys($row);
        $firstkey = $firstkey[0];
        $key = $row[$firstkey];
        unset($row[$firstkey]);
        $newarray[$key][] = $row;
    }
    return $newarray;
}

?>

Example:

<?

$array =
Array(
    0 => Array('color' => 'red','name' => 'apple', 'quantity' => '3'),
    1 => Array('color' => 'green','name' => 'pear', 'quantity' => '2'),
    2 => Array('color' => 'yellow','name' => 'corn', 'quantity' => '3'),
    3 => Array('color' => 'blue','name' => 'grape', 'quantity' => '4'),
    4 => Array('color' => 'yellow','name' => 'banana', 'quantity' => '13'),
);

$output = groupbyfirst($array);
print_r($output);

?>

will return:

Array
(
 [red] => Array ( [0] => Array ( [name] => apple [quantity] => 3 ) )
 [green] => Array ( [0] => Array ( [name] => pear [quantity] => 2 ) )
 [yellow] => Array ( [0] => Array ( [name] => corn [quantity] => 3 ), [1] => Array ( [name] => banana [quantity] => 13 ) )
 [blue] => Array ( [0] => Array ( [name] => grape [quantity] => 4 ))
)

Or you can use mysql recordset:

<?
while ($row=mysql_fetch_array($result,MYSQL_ASSOC))
{
    $firstkey = array_keys($row);
    $firstkey = $firstkey[0];
    $key = $row[$firstkey];
    unset($row[$firstkey]);
    $newarray[$key][] = $row;
}
?>

aidan at php dot net (21-May-2004 03:15)

This functionality is now implemented in the PEAR package PHP_Compat.

More information about using this function without upgrading your version of PHP can be found on the below link:

http://pear.php.net/package/PHP_Compat