array_combine
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
Array of keys to be used. Illegal values for key will be converted to string .
Array of values to be used
Return Values
Returns the combined array .
Errors/Exceptions
As of PHP 8.0.0, a ValueError is thrown if the number of elements in keys and values does not match. Prior to PHP 8.0.0, a E_WARNING was emitted instead.
Changelog
| Version | Description |
|---|---|
| 8.0.0 | array_combine() will now throw a ValueError if the number of elements for each array is not equal; previously this function returned false instead. |
Examples
Example #1 A simple array_combine() example
$a = array( ‘green’ , ‘red’ , ‘yellow’ );
$b = array( ‘avocado’ , ‘apple’ , ‘banana’ );
$c = array_combine ( $a , $b );
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 supplied function to every member of an array
- array_values() — Return all the values of an array
- array_map() — Applies the callback to the elements of the given arrays
User Contributed Notes 22 notes
If two keys are the same, the second one prevails.
Example:
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:
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
)
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
function array_combine_ ( $keys , $values ) $result = array();
foreach ( $keys as $i => $k ) $result [ $k ][] = $values [ $i ];
>
array_combine() has a strange bug/misfeature (as of PHP 5.3.2): There is no logical reason for throwing a warning and returning FALSE, instead of returning (see http://bugs.php.net/bug.php?id=34857). Here is a quick workaround:
function array_real_combine ( $a , $b )
return $a ===array() && $b ===array() ? array() : array_combine ( $a , $b );
>
?>
// 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 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)));
If two keys are the same, the second one prevails.
Example:
print_r ( array_combine (Array( ‘a’ , ‘a’ , ‘b’ ), Array( 1 , 2 , 3 )));
?>
Returns:
Array
(
[a] => 2
[b] => 3
)
I recently had to flip an array and group the elements by value, this snippet will do that:
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:
$users_countries = array(
‘username1’ => ‘US’ ,
‘user2’ => ‘US’ ,
‘newuser’ => ‘GB’
);
print_r ( flipAndGroup ( $users_countries ));
?>
Returns:
Array
(
[US] => Array
(
[0] => username1
[1] => user2
)
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.
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
)
(
[SMART Board] => serials to smart board 2
[Projector] => serials to projector 2
[Speakers] => serials to speakers 2
[Splitter] => serials to splitter 2
)
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 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()
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 needed a function that truncated extra values, and only went as far as keys without throwing a warning as array_combine does.
function safeArrayCombine ( $keys , $values ) <
$combinedArray = array();
for ( $i = 0 , $keyCount = count ( $keys ); $i < $keyCount ; $i ++) <
$combinedArray [ $keys [ $i ]] = $values [ $i ];
>
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.
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 )
/* 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 */
?>
Here a way to manage no uniqueness keys case. Values of duplicate keys are put in an array.
function array_combine_multi (array $keys , array $values )
if ( count ( $keys ) !== count ( $values )) throw new Exception ( ‘Arrays count mismatch’ );
>
$result = [];
foreach ( $values as $i => $value ) if (!isset( $result [ $keys [ $i ]])) $result [ $keys [ $i ]] = $value ;
> elseif (! is_array ( $result [ $keys [ $i ]])) $result [ $keys [ $i ]] = [ $result [ $keys [ $i ]], $value ];
> else <
$result [ $keys [ $i ]][] = $value ;
>
>
return $result ;
>
$keys = [ ‘key-1’ , ‘key-2’ , ‘key-3’ , ‘key-2’ , ‘key-2’ ];
$values = [ ‘value-1’ , ‘value-2’ , ‘value-3’ , ‘value-4’ , ‘value-5’ ];
$result = array_combine_multi ( $keys , $values );
print_r ( $result );
Array (
Php конкатенация элементов массива => value-1
Php конкатенация элементов массива => Array (
[0] => value-2
[1] => value-4
[2] => value-5
)
Php конкатенация элементов массива => value-3
)
*/