PHP 5.6.0 released

array_combine

(PHP 5)

array_combineCrea un nuevo array, usando una matriz para las claves y otra para sus valores

Descripción

array array_combine ( array $keys , array $values )

Crea un array usando los valores del array keys como las keys y los valores del array values como los valores correspondientes.

Parámetros

keys

Array de las keys a usar. Cualquier valor inválido para la key será convertido a string.

values

Array de valores a usar

Valores devueltos

Retorna el array combinado, FALSE si el número de elementos de cada array no es igual.

Errores/Excepciones

Arroja un E_WARNING si el número de elementos en keys y values no coincide.

Historial de cambios

Versión Descripción
5.4.0 Versiones previas emiten un E_WARNING y devuelven FALSE para arrays vacíos.

Ejemplos

Ejemplo #1 Ejemplo simple de array_combine()

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

print_r($c);
?>

El resultado del ejemplo sería:

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

Ver también

add a note add a note

User Contributed Notes 16 notes

up
24
loureirorg at gmail dot com
1 year ago
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
)
up
6
zequez at gmail dot com
3 years ago
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
)
up
6
quecoder at gmail
6 years ago
<?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 )
?>
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3
dejiakala at gmail dot com
2 years ago
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, $b);
}
?>
up
4
claude dot pache at gmail dot com
4 years ago
array_combine() has a strange bug/misfeature (as of PHP 5.3.2): There is no logical reason for <? array_combine(array(), array()) ?> throwing a warning and returning FALSE, instead of returning <? array() ?> (see http://bugs.php.net/bug.php?id=34857). Here is a quick workaround:
<?php
function array_real_combine($a, $b)
{
    return
$a===array() && $b===array() ? array() : array_combine($a, $b);
}
?>
up
4
Khaly
6 years ago
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
}

?>
up
3
neoyahuu at yahoo dot com
7 years ago
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
)
up
1
g.REMOVETHIS.vincendon AT vithemis.com
2 years ago
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);
       
       
/* Checking if arrays are on the same model (array('INDEX'=> array()) or array()) */
       
$check = count(array_unique(array_map('is_array',array_map('current',$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(); }
       
       
/* Checking the model of arrays, array('INDEX' => array()) or Array() */
       
$assocArray = is_array(array_shift(array_map('current',$arrays)));
       
       
/* If empty $Keys is given, we fill an empty array */
       
if (empty($keys)) $keys = array_keys(array_fill(0,max(($assocArray) ? array_map('count',array_map('current',$arrays)) : array_map('count',$arrays)),'foo'));

       
/* Init */
       
$ret=array();$i=0;
       
/* Cycling on each keys values, making an offset for each */
       
foreach($keys as $v)
        {
           
/* Cycling on arrays */
           
foreach ($arrays as $k)
            {
                if (
$assocArray)
                {
                   
/* Getting the index of the element */
                   
$key = key($k);
                   
/* If the offset exists, we place it */
                   
$ret[$v][$key] = isset($k[$key][$i]) ? $k[$key][$i]:false;
                }
               
/* Making the array with auto-made index */
               
else
                   
$ret[$v][] = isset($k[$i]) ? $k[$i]: false;
            }
           
/* Getting the next offset */
           
$i++;
        }
        return
$ret;
    }

   
/* Examples */
   
$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))); /* Associative index, associative subarray indexes */
    
print_r(array_combine_array($r,$a1,array('french' => $a2),array('spanish' => $a3))); /* Ouputs Error */
    
print_r(array_combine_array($r,$a1,$a2,$a3)); /* Associative index, auto-made subarray indexes */
    
print_r(array_combine_array(array(),array('english' => $a1),array('french' => $a2),array('spanish' => $a3))); /* Auto-made index, associative subarray indexes */
?>
up
0
ismorodin at hotmail dot com
2 months ago
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
up
-1
Dan LaManna
2 years ago
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;
}
?>
up
-1
aaron at aaronholmes dot net
1 year ago
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"
}
up
-3
J.D.D.
6 years ago
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 )
up
-2
bradentkeith at dot dontspam dot gmail dot com
4 years ago
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
        )

)
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-2
xavier at api-meal dot eu
4 years ago
<?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;
}
?>
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-2
Mike Jean
6 years ago
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.
up
-5
Anonymous
1 year ago
Here is the Better solutions for array combine :

http://www.myfric.com/blog/item/php-array-combine-key-and-value
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