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Last updated: Sat, 27 Jan 2007

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# array_diff

(PHP 4 >= 4.0.1, PHP 5)

array_diff -- Вычислить расхождение в массивах

## Описание

array array_diff ( array array1, array array2 [, array ...] )

Функция array_diff() возвращает массив, состоящий из значений массива `array1`, которые отсутствуют в любом другом массиве, перечисленном в последующих аргументах. Обратите внимание, что ключи массивов сохраняются.

Пример 1. Пример использования array_diff()

`$array1 = array ("a" => "green", "red", "blue", "red"); $array2 = array ("b" => "green", "yellow", "red"); $result = array_diff ($array1, $array2);`

В результате выполнения этой программы переменная `$result` будет содержать `array ("blue");`. Повторения одного и того же значения в $array1 обрабатываются как одно значение.

> Замечание: Два элемента считаются одинаковыми если и только если `(string) $elem1 === (string) $elem2`. Другими словами, когда их строковое представление идентично.

> Замечание: Обратите внимание, что эта функция обрабатывает только одно измерение n-размерного массива. Естественно, вы можете обрабатывать и более глубокие уровни вложенности, например, используя `array_diff($array1[0], $array2[0]);`.

Внимание

См.также array_intersect().

add a note User Contributed Notes
array_diff
ahigerd at stratitec dot com
01-Feb-2007 02:30
`An earlier comment suggested using array_merge() to reindex the array. While this will work, array_values() is about 30-40% faster and accomplishes the same task.`
03-Aug-2006 12:30
`array_diff provides a handy way of deleting array elements by their value, without having to unset it by key, through a lengthy foreach loop and then having to rekey the array.
<?php
//pass value you wish to delete and the array to delete from
function array_delete( $value, $array)
{
$array = array_diff( $array, array($value) );
return $array;
}
?>`
Colin
25-Jul-2006 09:44
`Undocumented return: it appears this will return NULL if an error occurs (e.g., an argument is not an array) and is not caught.
<?
@array_diff(NULL, array(1));
@array_diff(array(1), NULL);
@array_diff();
?>
All return NULL. (Note the "@")`
ben dot lancaster at design-ontap dot co dot uk
07-Jul-2006 04:57
`One common caveat of this function is that if the arrays match, an empty array is return, not a strict boolean. E.g.:
<?php
$array1 = $array2 = array('a','b','c');
var_dump(array_diff($array1,$array2));
/*
*Returns:
* array(0) {
* }
*/
?>`
pavlicic at NOSPAM dot hotmail dot com
09-Mar-2006 01:55
`<?php
// first array
$vid_player = $vm->getVideosByPlayer($player);
// second array
$vid_playlist = $vm->getVideosByPlaylist($playlist);
// this will not work...
$vid_player = array_diff($vid_player, $vid_playlist);
// but if you do this first...
$videos = array();
foreach ( $vid_player as $player )
{
if ( $vid_playlist != null )
{
foreach ( $vid_playlist as $video )
{
if ( $player->id == $video->id )
$videos[] = $player;
}
}
}
// this will work...
$vid_player = array_diff($vid_player, $videos);
?>
The first array_diff() compares two arrays only to find out that all the objects are unique!`
Jappie
22-Jan-2006 10:40
`Sorry for the bug in my last comment (probably rightfully removed by the admins).
If you want to compare more than 2 arrays, or don't know how many arrays need to be compared, this is your function:
<?php
# An extention to array_diff:
# It returns an array of all values not present in all arrays given. If '$strict' is true,
# it returns all values not present or not in the same order in all arrays given. The
# arrays to compare must be placed in another array, which is used as argument '$arrays'.
# Returns false if the '$arrays' is invalid.
function array_rdiff ($arrays, $strict = false) {
# check if argument is valid.
if (!is_array ($arrays))
return false;
foreach ($arrays as $array)
if (!is_array ($array))
return false;
# set working variables
$diff = array ();
$amount = count ($arrays);
$needles = array_shift ($arrays);
# compare
for ($n = 0; $n < $amount; $n++) {
for ($m = 0; $needles[$m]; $m++) {
$found = true;
$positions = array ($m);
foreach ($arrays as $haystack) {
if (($pos = array_search ($needles[$m], $haystack)) === false)
$found = false;
if ($strict)
$positions[] = $pos;
}
if (!$found)
$diff[] = $needle;
elseif ($strict && (count (array_unique ($positions)) > 1))
$diff[] = $needle;
}
$arrays[] = $needles;
$needles = array_shift ($arrays);
}
return array_unique ($diff);
}
?>`
Simon Riget at paragi.dk
21-Jan-2006 05:27
`A simple multidimentional key aware array_diff function.
<?php
function arr_diff($a1,$a2){
foreach($a1 as $k=>$v){
unset($dv);
if(is_int($k)){
// Compare values
if(array_search($v,$a2)===false) $dv=$v;
else if(is_array($v)) $dv=arr_diff($v,$a2[$k]);
if($dv) $diff[]=$dv;
}else{
// Compare noninteger keys
if(!$a2[$k]) $dv=$v;
else if(is_array($v)) $dv=arr_diff($v,$a2[$k]);
if($dv) $diff[$k]=$dv;
}
}
return $diff;
}
?>
This function meets my immidiate needs but I'm shure it can be improved.`
doug at NOSPAM dot thrutch dot co dot uk
06-Jan-2006 04:22
`After spending half an hour scratching my head wondering why this function wasn't working I realised I had the arguments the wrong way round!
I needed to remove the contents of $array1 from $array2 so I tried:
<?php
$diff = array_diff($members1, $members2);
?>
WRONG!! A quick swap around and things worked smoothly...
<?php
$diff = array_diff($members2, $members1);
?>
Hope this saves someone a bit of bother`
air at multi dot fi
04-Jan-2006 03:41
`A small thing that caused me trouble today, wich I don't see listed on this page is that array_diff keeps the placing for the uniqe values, and removes the duplicated. This gives us empty fields in the array, wich caused me a lot of trouble. The solutions was simply to use array_merge() around the array_diff.
For example:
$array1 = array('blue', 'red', 'green');
$array2 = array('red');
array_diff($array1, $array2);
Will give us:
------
Array
(
[0] => red
[1] =>
[2] => green
)
But if we use:
array_merge(array_diff($array1, $array2));
We will get:
------
Array
(
[0] => red
[1] => green
)`
Viking Coder
03-Jan-2006 09:07
`To anybody wanting a double-sided array_diff - mentioned by rudigier at noxx dot at. Remember, array_diff gives you everything in the first array that isn't in the subsequent arrays.
$array1=array('blue','red','green');
$array2=array('blue','yellow','green');
array_merge(array_diff($array1, $array2),array_diff($array2, $array1));
Result
------
Array
(
[0] => red
[1] => yellow
)`
white_phoenix at ru dot ru
14-Dec-2005 11:37
`To: effectpenguin at antarctida dot ru
Re: interesting effect
<?php
function arraycpy(&$target,&$array)
{
if (!is_array($target)) {$target = array();}
foreach($array as $k=>$v) {if ($k != "GLOBALS") {$target[$k] = $v;}}
}
arraycpy($old,$GLOBALS);
// some actions with variables:
$homer = "beer";
arraycpy($new,$GLOBALS);
$diff = array_diff($new,$old);
var_dump($diff);
?>
array(1) {
["homer"]=>
string(4) "beer"
}
Windows NT WPX_NB 5.1 build 2600 PHP/5.0.4`
penguin at antarctida dot ru
06-Oct-2005 05:41
`Interesting effect...
I just wanted to see, what variables are created and not unset after some actions.
So I write:
<?php
$a_var_GlobalsBefore = $GLOBALS;
?>
...some actions with variables
<?php
$a_var_GlobalsAfter = $GLOBALS;
$a_var_VariablesNotUnset = array_diff ($a_var_GlobalsAfter, $a_var_GlobalsBefore);
?>
...and _ALL_ variables puff up in smoke.
Have no idea what causes this behavior, but found a nice workaround:
<?php
$a_var_GlobalsBefore = array_keys ($GLOBALS);
?>
...some actions with variables
<?php
$a_var_GlobalsAfter = array_keys ($GLOBALS);
$a_var_VariablesNotUnset = array_diff ($a_var_GlobalsAfter, $a_var_GlobalsBefore);
?>
...and the unset variables are here.`
rafmav
19-Apr-2005 04:24
`Here is a few functions to do a fast diff between two arrays in a few lines.
You can use it with other functions described in the function array_merge : array_merge_replace from an other user, and two functions using it : array_merge_diff and array_merge_diff_reverse.
Note that the keys are preserved!
<?
// returns a two dimensions array with the deleted data
// and the added data
function array_diff_both($new,$old)
{
$del=array_diff_assoc($old,$new);
$add=array_diff_assoc($new,$old);
return $diff=array("del"=>$del, "add"=>$add);
}
// returns a two dimensions array with the equal data,
// deleted data and the added data
function array_diff_all($arr_new,$arr_old)
{
$arr_equ=array_intersect_assoc($arr_new,$arr_old);
$arr_del=array_diff_assoc($arr_old,$arr_new);
$arr_add=array_diff_assoc($arr_new,$arr_old);
return $diff=array("equ"=>$arr_equ, "del"=>$arr_del, "add"=>$arr_add);
}
?>`
rudigier at noxx dot at
09-Feb-2005 10:53
`if you don't like the php diff (like me) then take look at my diff functions
if you have two arrays, lets say:
a1 = { blue, red, green }
a2 = { blue, yellow, green }
array_diff just gives me nothing, although there is a difference. instead of an empty array, i needed an array which should contain "red" and "yellow" in this case.
single_diff satisfies my wish.
function single_diff(&$a1,&$a2)
{
$r = array(); // return
foreach ($a1 as $pl) // payload
{
if (! in_array($pl, $a2, true) )
$r[] = $pl;
}
foreach ($a2 as $pl) // payload
{
if (! in_array($pl, $a1, true) && ! in_array($pl, $r, true) )
$r[] = $pl;
}
return $r;
}
--------------------
this one just keeps the keys of the arrays in mind by comparing the values directly. just in case if there are values, which might occur multiple in one of these arrays.
function single_diff_assoc(&$a1,&$a2)
{
$r = array(); // return
foreach ($a1 as $k => $pl) // payload
{
if (! isset($a2[$k]) || $a2[$k] != $pl)
$r[$k] = $pl;
}
foreach ($a2 as $k => $pl) // payload
{
if ( (! isset($a1[$k]) || $a1[$k] != $pl ) && ! isset($r[$k]) )
$r[$k] = $pl;
}
return $r;
}
recursion support might be useful, but feel free to modify this functions to your own purposes.`
j dot j dot d dot mol at ewi dot tudelft dot nl
31-Dec-2004 12:34
`Here is some code to take the difference of two arrays. It allows custom modifications like prefixing with a certain string (as shown) or custom compare functions.
<?php
// returns all elements in $all which are not in $used in O(n log n) time.
// elements from $all are prefixed with $prefix_all.
// elements from $used are prefixed with $prefix_used.
function filter_unused( $all, $used, $prefix_all = "", $prefix_used = "" ) {
$unused = array();
// prefixes are not needed for sorting
sort( $all );
sort( $used );
$a = 0;
$u = 0;
$maxa = sizeof($all)-1;
$maxu = sizeof($used)-1;
while( true ) {
if( $a > $maxa ) {
// done; rest of $used isn't in $all
break;
}
if( $u > $maxu ) {
// rest of $all is unused
for( ; $a <= $maxa; $a++ ) {
$unused[] = $all[$a];
}
break;
}
if( $prefix_all.$all[$a] > $prefix_used.$used[$u] ) {
// $used[$u] isn't in $all?
$u++;
continue;
}
if( $prefix_all.$all[$a] == $prefix_used.$used[$u] ) {
// $all[$a] is used
$a++;
$u++;
continue;
}
$unused[] = $all[$a];
$a++;
}
return $unused;
}
?>`
sire at coolquotescollection dot com
25-Nov-2003 05:52
`Continuing from r.kirschke's excellent diff function (above), here's a function that will turn the result into nicely formatted HTML:
<?php
echo "<html><body bgcolor=white>";
$oldString = "Once there was a boy named Bart and a girl named Lisa.";
$newString = "Once upon a time there was a girl named Lisa.";
echo "Old String: " . $oldString . "<br>";
echo "New String: " . $newString . "<br>";
echo "Difference: " . diff_to_html($oldString, $newString);
// Returns a nicely formatted html string
function diff_to_html($oldString, $newString)
{
$a1 = explode(" ", $oldString);
$a2 = explode(" ", $newString);
$result = arr_diff($a1, $a2);
foreach ($result[0] as $num => $foo)
{
$source = $result[1][$num];
$element = $result[0][$num];
switch ($source)
{
case "1":
$pre = "<font color=red><s>";
$post = "</s></font>";
break;
case "2":
$pre = "<font color=green>";
$post = "</font>";
break;
case "b":
$pre = "";
$post = "";
break;
}
// VERTICAL OUTPUT:
// $return .= $num . $pre . " " . $source .
// " " . $element . $post . "<br>";
// READABLE OUTPUT:
$return .= $pre . $element . $post . " ";
}
return $return;
}
?>`
18-Nov-2003 04:54
`From the page:
Note: Please note that this function only checks one dimension of a n-dimensional array. Of course you can check deeper dimensions by using array_diff($array1[0], $array2[0]);
I've found a way to bypass that. I had 2 arrays made of arrays.
I wanted to extract from the first array all the arrays not found in the second array. So I used the serialize() function:
<?php
function my_serialize(&$arr,$pos){
$arr = serialize($arr);
}
function my_unserialize(&$arr,$pos){
$arr = unserialize($arr);
}
//make a copy
$first_array_s = $first_array;
$second_array_s = $second_array;
// serialize all sub-arrays
array_walk($first_array_s,'my_serialize');
array_walk($second_array_s,'my_serialize');
// array_diff the serialized versions
$diff = array_diff($first_array_s,$second_array_s);
// unserialize the result
array_walk($diff,'my_unserialize');
// you've got it!
print_r($diff);
?>`
d dot u dot phpnet at holomind dot de
26-Mar-2003 11:48
`I was not satisfied with the compare-funtions of array_diff() so i wrote a litte diff-clone which compares arrays and shows all different entries. You can easliy change the function formatline() for your needs.
function arr_diff( $a1, $a2, $show_matches=0);
...
output:
1 : 1 : - <head><title>Text</title></head>
1 : 1 : + <head><title>Text2</title></head>
4 : 4 : - code b
4 : 4 : + code a
8 : 8 : - code f
See details on: (example and source)
http://www.holomind.de/phpnet/diff.php
http://www.holomind.de/phpnet/diff.src.php`
r dot kirschke at gmx dot net
24-Mar-2003 01:26
`Are you looking for a function which returns an edit script (a set of insert and delete instructions on how to change one array into another)? At least, that's what I hoped to find here, so here's some code based on http://www.cs.arizona.edu/people/gene/PAPERS/diff.ps :
<?php
function diff_rek(&$a1,&$a2,$D,$k,&$vbck)
{
$x=$vbck[$D][$k]; $y=$x-$k;
if ($D==0)
{
if ($x==0) return array(array(),array());
else
return array(array_slice($a1,0,$x),array_fill(0,$x,"b"));
}
$x2=$vbck[$D-1][$k+1];
$y2=$vbck[$D-1][$k-1]-($k-1);
$xdif=$x-$x2; $ydif=$y-$y2;
$l=min($x-$x2,$y-$y2);
$x=$x-$l;
$y=$y-$l;
if ($x==$x2)
{
$res=diff_rek($a1,$a2,$D-1,$k+1,$vbck);
array_push($res[0],$a2[$y-1]);
array_push($res[1],"2");
if ($l>0)
{
$res[0]=array_merge($res[0],array_slice($a2,$y,$l));
$res[1]=array_merge($res[1],array_fill(0,$l,"b"));
}
}
else
{
$res=diff_rek($a1,$a2,$D-1,$k-1,$vbck);
array_push($res[0],$a1[$x-1]);
array_push($res[1],"1");
if ($l>0)
{
$res[0]=array_merge($res[0],array_slice($a1,$x,$l));
$res[1]=array_merge($res[1],array_fill(0,$l,"b"));
}
}
return $res;
}
function arr_diff(&$a1,&$a2)
{
$max=70;
$c1=count($a1);
$c2=count($a2);
$v[1]=0;
for ($D=0; $D<=$max; $D++)
{
for ($k=-$D; $k<=$D; $k=$k+2)
{
if (($k==-$D) || ($k!=$D && $v[$k-1]<$v[$k+1]))
$x=$v[$k+1];
else
$x=$v[$k-1]+1;
$y=$x-$k;
while (($x<$c1)&&($y<$c2)&&($a1[$x]==$a2[$y]))
{
$x++;
$y++;
}
$v[$k]=$x;
if (($x>=$c1)&&($y>=$c2))
{
$vbck[$D]=$v;
return diff_rek($a1,$a2,$D,$c1-$c2,$vbck);
};
}
$vbck[$D]=$v;
};
return -1;
}
?>
This works on arrays of all elements for which the operator "==" is defined.
arr_dif($a1,$a2) returns an array of two arrays:
$result[0] = array of elements from $a1 and $a2
$result[1] = array of chars - one for each element from $result[0]:
"1" : The corresponding element is from $a1
"2" : The corresponding element is from $a2
"b" : The correspondig element is from both source arrays
The function returns -1, when the number of different elements is greater than $max
Example:
$a1=array("hello","world");
$a2=array("good","bye","world");
=> arr_diff($a1,$a2) = array(array("hello","good","bye","world"), array("1","2","2","b"));`
csaba2000 at yahoo dot com
25-Feb-2003 01:58
`<?php
function array_key_diff($ar1, $ar2) { // , $ar3, $ar4, ...
// returns copy of array $ar1 with those entries removed
// whose keys appear as keys in any of the other function args
$aSubtrahends = array_slice(func_get_args(),1);
foreach ($ar1 as $key => $val)
foreach ($aSubtrahends as $aSubtrahend)
if (array_key_exists($key, $aSubtrahend))
unset ($ar1[$key]);
return $ar1;
}
$a = array("c" => "catty", "b" => "batty", "a" => "aunty", 5 => 4, 2.9 => 7, 11, "n" => "nutty");
$b = array(9, "d" => "ditty", "b" => "bratty", "a" => null, 10, 13);
$c = array_key_diff ($a, $b, array(5 => 6));
?>
$c is then equivalent to array('c' => 'catty', 6 => 11, 'n' => 'nutty')
Csaba Gabor from New York`
ds2u at the hotmail dot com
23-Feb-2003 04:22
`Yes you can get rid of gaps/missing keys by using:
<?php
$result = array_values(array_diff($array1,$array2));
?>
But to drop the storage of void spaces (actually a line feed) which are irritatingly indexed when reading from files - just use difference:
<?php
$array = array ();
$array[0] = "\n";
$result = array_diff($result,$array);
?>
dst`
jg at sto dot com dot au
02-Nov-2002 01:54
`I have found an interesting use for array_diff. I remember seing somebody having trouble deleting from an array because it left "holes".
I thought about using array_diff to fix the problem. Try running this code and see what it does:
<?php
for($i=0;$i<4;$i++)
{
print("Deleting item $i from the array<BR>");
$my_array = array("value1","value2","value3","value4");
$my_array = array_diff($my_array,array_slice($my_array,$i,1));
foreach($my_array as $value)print(" -->$value<BR>\n");
}
?>
It seems to work for every member of the array. I'm not sure how efficient it would be on really large arrays, though.
JG Estiot`
drNOSPAMtdiggersSPAMNO at hotmail dot com
06-Aug-2002 01:10
`array_diff does not have buggy behavior as described above. The problem stems from calling array_diff() each time in the loop, therefore regererating a new array with an index always at the beginning EVERY time, so each will always pick the first entry. This is not buggy, but in fact what you've told the program to do :) The solution is not as much a solution, but properly instructing the program what to do!
Cheers!
TheoDiggers`
arjanz at intermax dot nl
09-Apr-2002 11:53
`In PHP 4.0.6 the array_minus_array() as shown above didn't work properly, especially when you use duplicated values:
When I wanted to substract
'Array(1,1,2,3)'
with
'Array (1,2,4)'
I wanted as result:
'Array(1,3)'
And not just 'Array (3)' as it would give using array_diff(), or nothing as result using the above array_minus_array function.
This worked for me:
<?php
function array_minus_array($a,$b) {
$c = Array();
foreach ($a as $key => $val) {
$posb = array_search($val,$b);
if (is_integer($posb)) {
unset($b[$posb]);
} else {
$c[] = $val;
}
}
return $c;
}
?>`
alex at bacan dot cl_remove_this_for_email
08-Feb-2002 12:03
`For those who are looking how to substract one array for another:
you cannot use the "-" operator !!!
But you can use this function:
<?php
function array_minus_array($a, $b) {
$c=array_diff($a,$b);
$c=array_intersect($c, $a);
return $c;
}
?>
So, for example:
<?php
$a[]="a";
$a[]="b";
$a[]="c";
$b[]="a";
$c=array_minus_array($a,$b);
var_dump($c);
?>
Prints out:
array(2) {
[1]=>
string(1) "b"
[2]=>
string(1) "c"
}
which is $a-$b, as we wanted.
PD: you may also do a foreach ... if $a in_array $b ... but this is much more elegant !!!
Credits to A.Atala "mandrake", who knows everything about mathematic.`
SeanECoates at !donotspam!yahoo dot ca
16-Oct-2001 10:43
`I just came upon a really good use for array_diff(). When reading a dir(opendir;readdir), I _rarely_ want "." or ".." to be in the array of files I'm creating. Here's a simple way to remove them:
<?php
$someFiles = array();
$dp = opendir("/some/dir");
while($someFiles[] = readdir($dp));
closedir($dp);
$removeDirs = array(".","..");
$someFiles = array_diff($someFiles, $removeDirs);
foreach($someFiles AS $thisFile) echo $thisFile."\n";
?>
S`
caugustin at alcyonis dot nospam dot fr
26-Jul-2001 03:57
`In version 4.0.1 to 4.0.4, array_diff() works on array of array, but not anymore in version 4.0.5 and 4.0.6.<br>
According to php team :
When I wrote array_diff I didn't think of this use. It
worked by accident. array_diff was changed to avoid
some ordering problems. The way it was there was no well
defined ordering. Due to automatic type conversion, you
you would have 3d < 99 < 370 < 3d. This made
array_diff fail, this was fixed by always using string
comparisons. That doesn't work for arrays though.`
ylu at enreach dot com
18-May-2001 10:15
`To skip empty values, simply use:
$result = array_values(array_diff($array1,$array2));`
david at audiogalaxy dot com
08-Apr-2001 04:12
`Note that array_diff() considers the type of the array elements when it compares them.
If array_diff() doesn't appear to be working, check your inputs using var_dump() to make sure you're not trying to diff an array of integers with an array of strings.`
add a note
array_fill_keys array_diff_ukey

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