array_intersect_ukey
The built-in function returns wrong result when input arrays have duplicate values.
Here is a code that works correctly:
<?php
function array_intersect_fixed($array1, $array2) {
$result = array();
foreach ($array1 as $val) {
if (($key = array_search($val, $array2, TRUE))!==false) {
$result[] = $val;
unset($array2[$key]);
}
}
return $result;
}
?>
array_intersect
(PHP 4 >= 4.0.1, PHP 5)
array_intersect — Computes the intersection of arrays
Description
array array_intersect
( array
$array1
, array $array2
[, array $ ...
] )
array_intersect() returns an array
containing all the values of array1
that are present in all the arguments.
Note that keys are preserved.
Parameters
-
array1 -
The array with master values to check.
-
array2 -
An array to compare values against.
-
array -
A variable list of arrays to compare.
Return Values
Returns an array containing all of the values in
array1 whose values exist in all of the parameters.
Examples
Example #1 array_intersect() example
<?php
$array1 = array("a" => "green", "red", "blue");
$array2 = array("b" => "green", "yellow", "red");
$result = array_intersect($array1, $array2);
print_r($result);
?>
The above example will output:
Array
(
[a] => green
[0] => red
)
Notes
Note: Two elements are considered equal if and only if (string) $elem1 === (string) $elem2. In words: when the string representation is the same.
See Also
- array_intersect_assoc() - Computes the intersection of arrays with additional index check
- array_diff() - Computes the difference of arrays
- array_diff_assoc() - Computes the difference of arrays with additional index check
add a note
User Contributed Notes
array_intersect
dml at nm dot ru
20-May-2011 05:06
faharanik
30-Jun-2010 07:30
Here's my approach to intersection returning only the values present in all the arrays.
Note that each array must not contain duplicate values.
I don't know how effective it actually is, but perhaps it could help.
<?php
// $arrays - Array of arrays to intersect.
function calculate_intersection($arrays)
{
$intersection = Array();
for($checked_item = 0; $checked_item < count($arrays[0]); $checked_item++)
{
$occurrence = 1;
for($compared_array = 1; $compared_array < count($arrays); $compared_array++)
{
for($compared_item = 0; $compared_item < count($arrays[$compared_array]); $compared_item++)
{
if($arrays[0][$checked_item] == $arrays[$compared_array][$compared_item])
{
$occurrence++;
if($occurrence == count($arrays))
{
$intersection[] = $arrays[0][$checked_item];
}
}
}
}
}
return $intersection;
}
?>
Yohann
12-Apr-2010 04:36
I used array_intersect in order to sort an array arbitrarly:
<?php
$a = array('one', 'two', 'three', 'four', 'five', 'six', 'seven', 'height', 'nine', 'ten');
$b = array('four', 'one', 'height', 'five')
var_dump(array_intersect($a, $b);
?>
will output:
0 => 'one'
1 => 'four'
2 => 'five'
3 => 'height'
i hope this can help...
james -at- bandit.co -dot- nz
08-Apr-2010 06:07
I needed an array_intersect that would delete the intersecting values from the original array. Voila:
<?php
// array_intersect that splits the needle array into two - one filled with "intersected" results, and one filled with the remainder
function array_intersect_split(&$needle, $haystack, $preserve_keys = false) {
if(!is_array($needle) || !is_array($haystack)) return false;
$new_arr = array();
foreach($needle as $key => $value) {
if(($loc = array_search($value, $haystack))!==false) {
if(!$preserve_keys) $new_arr[] = $value;
else $new_arr[$key] = $value;
unset($needle[$key]);
}
}
return $new_arr;
}
?>
189780 at gmail dot com
02-Jan-2010 07:26
Actually array_intersect finds the dublicate values, here is my approach which is 5 times faster than built-in function array_intersect().. Give a try..
<?php
function my_array_intersect($a,$b)
{
for($i=0;$i<sizeof($a);$i++)
{
$m[]=$a[$i];
}
for($i=0;$i<sizeof($a);$i++)
{
$m[]=$b[$i];
}
sort($m);
$get=array();
for($i=0;$i<sizeof($m);$i++)
{
if($m[$i]==$m[$i+1])
$get[]=$m[$i];
}
return $get;
}
?>
Barış ÇUHADAR
[email protected]
Shawn Pyle
13-Aug-2009 09:29
array_intersect handles duplicate items in arrays differently. If there are duplicates in the first array, all matching duplicates will be returned. If there are duplicates in any of the subsequent arrays they will not be returned.
<?php
array_intersect(array(1,2,2),array(1,2,3)); //=> array(1,2,2)
array_intersect(array(1,2,3),array(1,2,2)); //=> array(1,2)
?>
gary
21-Jun-2009 12:57
i wrote this one to get over the problem i found in getting strings intersected instead of arrays as there is no function in php.
<?php
function matched_main_numbers($string, $string2)
{
$string = "04 16 17 20 29";
$arr1 = explode(" ", $string);
$string2 = "45 34 04 29 16";
$arr2 = explode(" ", $string2);
$array = array_intersect($arr1, $arr2);
$comma_separated = implode($array);
$str = $comma_separated;
$balls = "$comma_separated";
$matched_balls = chunk_split($balls,2," ");
$matched_balls =" $matched_balls";
$number_of_matched_main_balls = strlen($str);
$number_of_matched_main_balls = ($number_of_matched_main_balls/2);
$numbers = "You matched $number_of_matched_main_balls main balls";
return $numbers;
}
?>
Oto Brglez
10-Mar-2009 07:02
If you wish to create intersection with arrays that are empty. Than the result of intersection is empty array.
If you wish to change this. I sugest that you do this.
It simply "ignores" empty arrays. Before loop use 1st array.
<?php
$a = array();
$a[] = 1;
$a[] = 2;
$a[] = 3;
$b = array();
$b[] = 4;
$b[] = 5;
$b[] = 1;
$c = array();
$c[] = 1;
$c[] = 5;
$d = array();
$kb=array('a','b','c','d');
$out = $a;
foreach($kb as $k){
if(!empty(${$k})) $out = array_intersect($out,${$k});
};
print_r($out);
// The result is array
// The result is empty array
print_r(array_intersect($a,$b,$c,$d));
?>
karl at libsyn dot com
30-Jan-2009 09:58
Given a multidimensional array that represents AND/OR relationships (example below), you can use a recursive function with array_intersect() to see if another array matches that set of relationships.
For example: array( array( 'red' ), array( 'white', 'blue' ) ) represents "red OR ( white AND blue )". array( 'red', array( 'white', 'blue' ) ) would work, too, BTW.
If I have array( 'red' ) and I want to see if it matches the AND/OR array, I use the following function. It returns the matched array,
but can just return a boolean if that's all you need:
<?php
$needle = array( array( 'red' ), array( 'white', 'blue' ) );
$haystack = array( 'red' );
function findMatchingArray( $needle, $haystack ) {
foreach( $needle as $element ) {
$test_element = (array) $element;
if( count( $test_element ) == count( array_intersect( $test_element, $haystack ) ) ) {
return $element;
}
}
return false;
}
?>
Pretty tough to describe what I needed it to do, but it worked. I don't know if anyone else out there needs something like this, but hope this helps.
Esfandiar -- e.bandari at gmail dot com
10-Aug-2008 12:44
Regarding array union: Here is a faster version array_union($a, $b)
But it is not needed! See below.
<?php
// $a = 1 2 3 4
$union = // $b = 2 4 5 6
array_merge(
$a,
array_diff($b, $a) // 5 6
); // $u = 1 2 3 4 5 6
?>
You get the same result with $a + $b.
N.B. for associative array the results of $a+$b and $b+$a are different, I think array_diff_key is used.
Cheers, E
stuart at horuskol dot co dot uk
07-Jul-2008 03:57
A clearer example of the key preservation of this function:
<?php
$array1 = array(2, 4, 6, 8, 10, 12);
$array2 = array(1, 2, 3, 4, 5, 6);
var_dump(array_intersect($array1, $array2));
var_dump(array_intersect($array2, $array1));
?>
yields the following:
array(3) {
[0]=> int(2)
[1]=> int(4)
[2]=> int(6)
}
array(3) {
[1]=> int(2)
[3]=> int(4)
[5]=> int(6)
}
This makes it important to remember which way round you passed the arrays to the function if these keys are relied on later in the script.
Malte
10-Feb-2008 10:34
Extending the posting by Terry from 07-Feb-2006 04:42:
If you want to use this function with arrays which have sometimes the same value several times, it won't be checked if they're existing in the second array as much as in the first.
So I delete the value in the second array, if it's found there:
<?php
$firstarray = array(1, 1, 2, 3, 4, 1);
$secondarray = array(4, 1, 6, 5, 4, 1);
//array_intersect($firstarray, $secondarray): 1, 1, 1, 4
foreach ($firstarray as $key=>$value){
if (!in_array($value,$secondarray)){
unset($firstarray[$key]);
}else{
unset($secondarray[array_search($value,$secondarray)]);
}
}
//$firstarray: 1, 1, 4
?>
aaron
17-Dec-2006 09:36
this one will work with associative arrays. also an overwrite function to only replace those elements in the first array.
<?php
function array_union()
{
if (func_num_args() < 2) { return; }
$arrays = func_get_args();
$outputArray = array_shift($arrays);
$remaining = count($arrays);
for ($i=0; $i<$remaining; $i++)
{
$nextArray = $arrays[$i];
foreach ($nextArray as $key=>$value)
{
$outputArray[$key] = $value;
}
}
return $outputArray;
}
function array_overwrite()
{
if (func_num_args() < 2) { return; }
$arrays = func_get_args();
$outputArray = array_shift($arrays);
$remaining = count($arrays);
for ($i=0; $i<$remaining; $i++)
{
$nextArray = $arrays[$i];
foreach ($nextArray as $key=>$value)
{
if (array_key_exists($key, $outputArray)) { $outputArray[$key] = $value; }
}
}
return $outputArray;
}
?>
Niels
19-Sep-2006 04:53
Here is a array_union($a, $b):
<?php
// $a = 1 2 3 4
$union = // $b = 2 4 5 6
array_merge(
array_intersect($a, $b), // 2 4
array_diff($a, $b), // 1 3
array_diff($b, $a) // 5 6
); // $u = 1 2 3 4 5 6
?>
nthitz at gmail dot com
08-Jun-2006 09:09
I did some trials and if you know the approximate size of the arrays then it would seem to be a lot faster to do this <?php array_intersect($smallerArray, $largerArray); ?> Where $smallerArray is the array with lesser items. I only tested this with long strings but I would imagine that it is somewhat universal.
terry(-at-)shuttleworths(-dot-)net
07-Feb-2006 07:42
I couldn't get array_intersect to work with two arrays of identical objects, so I just did this:
foreach ($firstarray as $key=>$value){
if (!in_array($value,$secondarray)){
unset($firstarray[$key]);
}
}
This leaves $firstarray as the intersection.
Seems to work fine & reasonably quickly.
tom p
04-Nov-2005 06:54
If you store a string of keys in a database field and want to match them to a static array of values, this is a quick way to do it without loops:
<?
$vals = array("Blue","Green","Pink","Yellow");
$db_field = "0,2,3";
echo implode(", ", array_flip(array_intersect(array_flip($vals), explode(",", $db_field))));
// will output "Blue, Pink, Yellow"
?>
sapenov at gmail dot com
10-Jun-2005 01:11
If you need to supply arbitrary number of arguments
to array_intersect() or other array function,
use following function:
$full=call_user_func_array('array_intersect', $any_number_of_arrays_here);
SETS INTERSECTION
18-May-2005 11:19
$a = array(1,2,3,4,5,2,6,1); /* repeated elements --> $a is not a set */
$b = array(0,2,4,6,8,5,7,9,2,1); /* repeated elements --> $b is not a set */
$ua = array_merge(array_unique($a)); /* now, $a is a set */
$ub = array_merge(array_unique($b)); /* now, $b is a set */
$intersect = array_merge(array_intersect($ua,$ub));
Note: 'array_merge' removes blank spaces in the arrays.
Note: order doesn't matter.
In one line:
$intersect_a_b = array_merge(array_intersect(array_merge(array_unique($a)), array_merge(array_unique($b))));
Additions/corrections wellcome...
gRiNgO
drew at iws dot co dot nz
21-Apr-2005 08:04
Just a handy tip.
If you want to produce an array from two seperate arrays on their intersects, here you go:
<?
$a = array("branches","E_SHOP");
$b = array("E_SHOP","Webdirector_1_0");
print join("/",array_merge(array_diff($a, $b), array_intersect($a, $b), array_diff($b, $a)));
?>
Gives you:
/branches/E_SHOP/Webdirectory_1_0
blu at dotgeek dot org
14-Oct-2004 05:34
Note that array_intersect and array_unique doesnt work well with multidimensional arrays.
If you have, for example,
<?php
$orders_today[0] = array('John Doe', 'PHP Book');
$orders_today[1] = array('Jack Smith', 'Coke');
$orders_yesterday[0] = array('Miranda Jones', 'Digital Watch');
$orders_yesterday[1] = array('John Doe', 'PHP Book');
$orders_yesterday[2] = array('Z� da Silva', 'BMW Car');
?>
and wants to know if the same person bought the same thing today and yesterday and use array_intersect($orders_today, $orders_yesterday) you'll get as result:
<?php
Array
(
[0] => Array
(
[0] => John Doe
[1] => PHP Book
)
[1] => Array
(
[0] => Jack Smith
[1] => Coke
)
)
?>
but we can get around that by serializing the inner arrays:
<?php
$orders_today[0] = serialize(array('John Doe', 'PHP Book'));
$orders_today[1] = serialize(array('Jack Smith', 'Coke'));
$orders_yesterday[0] = serialize(array('Miranda Jones', 'Digital Watch'));
$orders_yesterday[1] = serialize(array('John Doe', 'PHP Book'));
$orders_yesterday[2] = serialize(array('Z� da Silva', 'Uncle Tungsten'));
?>
so that array_map("unserialize", array_intersect($orders_today, $orders_yesterday)) will return:
<?php
Array
(
[0] => Array
(
[0] => John Doe
[1] => PHP Book
)
)
?>
showing us who bought the same thing today and yesterday =)
[]s
tompittlik at disfinite dot net
24-Jun-2004 06:27
Just a small mod to ben's code to make it work properly:
<?php
if(sort(array_unique($b + $a)) === sort($b))
// $a is legit
}
?>
This is useful for checking for illegal characters in a username.
t dot wiltzius at insightbb dot com
23-Jun-2004 09:33
I needed to compare an array with associative keys to an array that contained some of the keys to the associative array. Basically, I just wanted to return only a few of the entries in the original array, and the keys to the entries I wanted were stored in another array. This is pretty straightforward (although complicated to explain), but I couldn't find a good function for comparing values to keys. So I wrote this relatively straightforward one:
<?php
function key_values_intersect($values,$keys) {
foreach($keys AS $key) {
$key_val_int[$key] = $values[$key];
}
return $key_val_int;
}
$big = array("first"=>2,"second"=>7,"third"=>3,"fourth"=>5);
$subset = array("first","third");
print_r(key_values_intersect($big,$subset));
?>
This will return:
Array ( [first] => 2 [third] => 3 )
anbolb at boltblue dot com
09-Jan-2004 01:11
This is also handy for testing an array for one of a series of acceptable elements. As a simple example, if you're expecting the query string to contain one of, say, user_id, order_id or item_id, to find out which one it is you could do this:
<?php
$valid_ids = array ('user_id', 'item_id', 'order_id');
if ($id = current (array_intersect ($valid_ids, array_keys ($_GET))))
{
// do some stuff with it
}
else
// error - invalid id passed, or none at all
?>
...which could be useful for constructing an SQL query, or some other situation where testing for them one by one might be too clumsy.
ben at kazez dot com
09-Dec-2003 10:49
To check whether an array $a is a subset of array $b, do the following:
<?php
if(array_unique($b + $a) === $b)
//...
?>
Actually, PHP ought to have a function that does this for you. But the above example works.
Alessandro Ranellucci alex at primafila dot net
16-Jul-2003 06:35
array_intersect($array1, $array2);
returns the same as:
array_diff($array1, array_diff($array1, $array2));
"inerte" is my hotmail.com username
26-Jun-2003 03:50
If you have a slow database query that uses JOIN, try to array_intersect() the table records.
I hung up my server countless times before using this function. Simple select from one table and put the records in an array ($records_1), then select records from any other table and put them in another array($records_2).
array_intersect() will emulate a JOIN for you.
<?php
$emulated_join = array_intersect($records_1, $records_2);
?>
Remember to test if it really offers a speed improvement, your mileage may vary (database type, hardware, version, etc...)
You could also emulate a JOIN from two text files, reading each line with the file() function.
david at audiogalaxy dot com
09-Apr-2001 04:54
Note that array_intersect() considers the type of the array elements when it compares them.
If array_intersect() doesn't appear to be working, check your inputs using var_dump() to make sure you're not trying to intersect an array of integers with an array of strings.