array_combine
(PHP 5)
array_combine — Creates an array by using one array for keys and another for its values
Description
array array_combine
( array
$keys
, array $values
)
Creates an array by using the values from the
keys array as keys and the values from the
values array as the corresponding values.
Parameters
-
keys -
Array of keys to be used. Illegal values for key will be converted to string.
-
values -
Array of values to be used
Return Values
Returns the combined array, FALSE if the number of elements
for each array isn't equal.
Errors/Exceptions
Throws E_WARNING if the number of elements in
keys and values does not
match.
Changelog
| Version | Description |
|---|---|
| 5.4.0 |
Previous versions issued E_WARNING and returned
FALSE for empty arrays.
|
Examples
Example #1 A simple array_combine() example
<?php
$a = array('green', 'red', 'yellow');
$b = array('avocado', 'apple', 'banana');
$c = array_combine($a, $b);
print_r($c);
?>
The above example will output:
Array
(
[green] => avocado
[red] => apple
[yellow] => banana
)
See Also
- array_merge() - Merge one or more arrays
- array_walk() - Apply a user function to every member of an array
- array_values() - Return all the values of an array
- PHP Руководство
- Функции по категориям
- Индекс функций
- Справочник функций
- Расширения, относящиеся к переменным и типам
- Массивы
- array_change_key_case
- array_chunk
- array_column
- array_combine
- array_count_values
- array_diff_assoc
- array_diff_key
- array_diff_uassoc
- array_diff_ukey
- array_diff
- array_fill_keys
- array_fill
- array_filter
- array_flip
- array_intersect_assoc
- array_intersect_key
- array_intersect_uassoc
- array_intersect_ukey
- array_intersect
- array_key_exists
- array_keys
- array_map
- array_merge_recursive
- array_merge
- array_multisort
- array_pad
- array_pop
- array_product
- array_push
- array_rand
- array_reduce
- array_replace_recursive
- array_replace
- array_reverse
- array_search
- array_shift
- array_slice
- array_splice
- array_sum
- array_udiff_assoc
- array_udiff_uassoc
- array_udiff
- array_uintersect_assoc
- array_uintersect_uassoc
- array_uintersect
- array_unique
- array_unshift
- array_values
- array_walk_recursive
- array_walk
- array
- arsort
- asort
- compact
- count
- current
- each
- end
- extract
- in_array
- key_exists
- key
- krsort
- ksort
- list
- natcasesort
- natsort
- next
- pos
- prev
- range
- reset
- rsort
- shuffle
- sizeof
- sort
- uasort
- uksort
- usort
Коментарии
<?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 )
?>
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 $arr4;
}
?>
Input:
Array
(
[0] => SMART Board
[1] => Projector
[2] => Speakers
[3] => Splitter
)
, Array
(
[0] => serial to smart board1
[1] => serial to projector 1
[2] => serial to speakers 1
[3] => serials to splitter 1
[4] => serials to smart board 2
[5] => serials to projector 2
[6] => serials to speakers 2
[7] => serials to splitter 2
)
Array
(
[0] => Array
(
[SMART Board] => serial to smart board1
[Projector] => serial to projector 1
[Speakers] => serial to speakers 1
[Splitter] => serials to splitter 1
)
[1] => Array
(
[SMART Board] => serials to smart board 2
[Projector] => serials to projector 2
[Speakers] => serials to speakers 2
[Splitter] => serials to splitter 2
)
)
array_combine() has a strange bug/misfeature (as of PHP 5.3.2): There is no logical reason for <? array_combine(array(), array()) ?> throwing a warning and returning FALSE, instead of returning <? array() ?> (see http://bugs.php.net/bug.php?id=34857). Here is a quick workaround:<?php
function array_real_combine($a, $b)
{
return $a===array() && $b===array() ? array() : array_combine($a, $b);
}
?>
If two keys are the same, the second one prevails.Example:
<?php
print_r(array_combine(Array('a','a','b'), Array(1,2,3)));
?>
Returns:
Array
(
[a] => 2
[b] => 3
)
I needed a function that truncated extra values, and only went as far as keys without throwing a warning as array_combine does.
<?php
function safeArrayCombine($keys, $values) {
$combinedArray = array();
for ($i=0, $keyCount = count($keys); $i < $keyCount; $i++) {
$combinedArray[$keys[$i]] = $values[$i];
}
return $combinedArray;
}
?>
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);
}
?>
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' => $a3))); /* Auto-made index, associative subarray indexes */
?>
If two keys are the same, the second one prevails.
Example:
<?php
print_r(array_combine(Array('a','a','b'), Array(1,2,3)));
?>
Returns:
Array
(
[a] => 2
[b] => 3
)
But if you need to keep all values, you can use the function below:
<?php
function array_combine_($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 $result;
}
print_r(array_combine_(Array('a','a','b'), Array(1,2,3)));
?>
Returns:
Array
(
[a] => Array
(
[0] => 1
[1] => 2
)
[b] => 3
)
I recently had to flip an array and group the elements by value, this snippet will do that:
<?php
function flipAndGroup($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
)
)
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;
}
?>
This will seem obvious to some, but if you need to preserve a duplicate key, being you have unique vars, you can switch the array_combine around, to where the vars are the keys, and this will output correctly.
This [default] formula auto-removes the duplicate keys.
$i=0;
foreach (array_combine($keys, $vars) as $key => $var)
{
$i=$i;
echo($key);
echo " ";
echo($var);
}
This formula accomplishes the same thing, in the same order, but the duplicate "keys" (which are now vars) are kept.
$i=0;
foreach (array_combine($vars, $keys) as $var => $key)
{
$i=$i;
echo($key);
echo " ";
echo($var);
}
I know, I'm a newbie, but perhaps someone else will need this eventually. I couldn't find another solution anywhere.
I had an epiphany when try to handle NON-ASSOCIATIVE array forms in my controller. This little one liner can pretty much edit ANY kind of non-associative array. For example this one just returns an array of values inputed by a new user.
The $data value is the the json_decoded() value of a register form.
Here is used str_replace, you could definitely do a number of things like preg matches and other things.
$readyToProcessForUser = array_combine(str_replace("new_user_", "", array_keys($data)), $data);
You could also do the same for the values.
$readyToProcessForUser = array_combine(array_keys($data), str_replace("-", "", $data));
Or BOTH!
Use full if you don't want to walk an entire array and the keys through the same callback.
$readyToProcessForUser = array_combine(array_walk('trim', array_keys($data)), array_walk('custom_callback', array_values($data)));
As of PHP 8.0, array_combine throws ValueError if the number of elements for each array is not equal;
To be on a safer side, you can perform a check instead.
$arrayk = array( 'key1', 'key2', 'key3' );
$arrayv = array( 'v1', 'v2', 'v3' );
if ( count( $arrayk ) === count( $arrayv ) ) {
echo '<pre>';
var_dump( array_combine( $arrayk, $arrayv ) );
echo '</pre>';
} else {
return false;
}