PHP 5.6.0 released

array_udiff

(PHP 5)

array_udiffComputes the difference of arrays by using a callback function for data comparison

Description

array array_udiff ( array $array1 , array $array2 [, array $... ], callable $value_compare_func )

Computes the difference of arrays by using a callback function for data comparison. This is unlike array_diff() which uses an internal function for comparing the data.

Parameters

array1

The first array.

array2

The second array.

value_compare_func

The callback comparison function.

The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second.

int callback ( mixed $a, mixed $b )

Return Values

Returns an array containing all the values of array1 that are not present in any of the other arguments.

Examples

Example #1 array_udiff() example using stdClass Objects

<?php
// Arrays to compare
$array1 = array(new stdclass, new stdclass,
                new 
stdclass, new stdclass,
               );

$array2 = array(
                new 
stdclass, new stdclass,
               );

// Set some properties for each object
$array1[0]->width 11$array1[0]->height 3;
$array1[1]->width 7;  $array1[1]->height 1;
$array1[2]->width 2;  $array1[2]->height 9;
$array1[3]->width 5;  $array1[3]->height 7;

$array2[0]->width 7;  $array2[0]->height 5;
$array2[1]->width 9;  $array2[1]->height 2;

function 
compare_by_area($a$b) {
    
$areaA $a->width $a->height;
    
$areaB $b->width $b->height;
    
    if (
$areaA $areaB) {
        return -
1;
    } elseif (
$areaA $areaB) {
        return 
1;
    } else {
        return 
0;
    }
}

print_r(array_udiff($array1$array2'compare_by_area'));
?>

The above example will output:

Array
(
    [0] => stdClass Object
        (
            [width] => 11
            [height] => 3
        )

    [1] => stdClass Object
        (
            [width] => 7
            [height] => 1
        )

)

Example #2 array_udiff() example using DateTime Objects

<?php
Class MyCalendar {
    public 
$free = array();
    public 
$booked = array();

    public function 
__construct($week 'now') {
        
$start = new DateTime($week);
        
$start->modify('Monday this week midnight');
        
$end = clone $start;
        
$end->modify('Friday this week midnight');
        
$interval = new DateInterval('P1D');
        foreach (new 
DatePeriod($start$interval$end) as $freeTime) {
            
$this->free[] = $freeTime;
        }
    }

    public function 
bookAppointment(DateTime $date$note) {
        
$this->booked[] = array('date' => $date->modify('midnight'), 'note' => $note);
    }

    public function 
checkAvailability() {
        return 
array_udiff($this->free$this->booked, array($this'customCompare'));
    }
    
    public function 
customCompare($free$booked) {
        if (
is_array($free)) $a $free['date'];
        else 
$a $free;
        if (
is_array($booked)) $b $booked['date'];
        else 
$b $booked;
        if (
$a == $b) {
            return 
0;
        } elseif (
$a $b) {
            return 
1;
        } else {
            return -
1;
        }
    }
}

// Create a calendar for weekly appointments
$myCalendar = new MyCalendar;

// Book some appointments for this week
$myCalendar->bookAppointment(new DateTime('Monday this week'), "Cleaning GoogleGuy's apartment.");
$myCalendar->bookAppointment(new DateTime('Wednesday this week'), "Going on a snowboarding trip.");
$myCalendar->bookAppointment(new DateTime('Friday this week'), "Fixing buggy code.");

// Check availability of days by comparing $booked dates against $free dates
echo "I'm available on the following days this week...\n\n";
foreach (
$myCalendar->checkAvailability() as $free) {
    echo 
$free->format('l'), "\n"
}
echo 
"\n\n";
echo 
"I'm busy on the following days this week...\n\n";
foreach (
$myCalendar->booked as $booked) {
    echo 
$booked['date']->format('l'), ": "$booked['note'], "\n"
}
?>

The above example will output:

I'm available on the following days this week...

Tuesday
Thursday


I'm busy on the following days this week...

Monday: Cleaning GoogleGuy's apartment.
Wednesday: Going on a snowboarding trip.
Friday: Fixing buggy code.

Notes

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_udiff($array1[0], $array2[0], "data_compare_func");.

See Also

  • array_diff() - Computes the difference of arrays
  • array_diff_assoc() - Computes the difference of arrays with additional index check
  • array_diff_uassoc() - Computes the difference of arrays with additional index check which is performed by a user supplied callback function
  • array_udiff_assoc() - Computes the difference of arrays with additional index check, compares data by a callback function
  • array_udiff_uassoc() - Computes the difference of arrays with additional index check, compares data and indexes by a callback function
  • array_intersect() - Computes the intersection of arrays
  • array_intersect_assoc() - Computes the intersection of arrays with additional index check
  • array_uintersect() - Computes the intersection of arrays, compares data by a callback function
  • array_uintersect_assoc() - Computes the intersection of arrays with additional index check, compares data by a callback function
  • array_uintersect_uassoc() - Computes the intersection of arrays with additional index check, compares data and indexes by a callback functions

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User Contributed Notes 7 notes

up
2
b4301775 at klzlk dot com
3 years ago
Quick example for using array_udiff to do a multi-dimensional diff

Returns values of $arr1 that are not in $arr2

<?php
$arr1
= array( array('Bob', 42), array('Phil', 37), array('Frank', 39) );
       
$arr2 = array( array('Phil', 37), array('Mark', 45) );
       
$arr3 = array_udiff($arr1, $arr2, create_function(
   
'$a,$b',
   
'return strcmp( implode("", $a), implode("", $b) ); ')
    );
       
print_r($arr3);
?>

Output:

Array
(
    [0] => Array
        (
            [0] => Bob
            [1] => 42
        )

    [2] => Array
        (
            [0] => Frank
            [1] => 39
        )

)
1

Hope this helps someone
up
2
Colin
8 years ago
I think the example given here using classes is convoluting things too much to demonstrate what this function does.

array_udiff() will walk through array_values($a) and array_values($b) and compare each value by using the passed in callback function.

To put it another way, array_udiff() compares $a[0] to $b[0], $b[1], $b[2], and $b[3] using the provided callback function.  If the callback returns zero for any of the comparisons then $a[0] will not be in the returned array from array_udiff().  It then compares $a[1] to $b[0], $b[1], $b[2], and $b[3].  Then, finally, $a[2] to $b[0], $b[1], $b[2], and $b[3].

For example, compare_ids($a[0], $b[0]) === -5 while compare_ids($a[1], $b[1]) === 0.  Therefore, $a[1] is not returned from array_udiff() since it is present in $b.

<?
$a
= array(
        array(
               
'id' => 10,
               
'name' => 'John',
               
'color' => 'red',
        ),
        array(
               
'id' => 20,
               
'name' => 'Elise',
               
'color' => 'blue',
        ),
        array(
               
'id' => 30,
               
'name' => 'Mark',
               
'color' => 'red',
        ),
);

$b = array(
        array(
               
'id' => 15,
               
'name' => 'Nancy',
               
'color' => 'black',
        ),
        array(
               
'id' => 20,
               
'name' => 'Elise',
               
'color' => 'blue',
        ),
        array(
               
'id' => 30,
               
'name' => 'Mark',
               
'color' => 'red',
        ),
        array(
               
'id' => 40,
               
'name' => 'John',
               
'color' => 'orange',
        ),
);

function
compare_ids($a, $b)
{
    return (
$a['id'] - $b['id']);
}
function
compare_names($a, $b)
{
    return
strcmp($a['name'], $b['name']);
}

$ret = array_udiff($a, $b, 'compare_ids');
var_dump($ret);

$ret = array_udiff($b, $a, 'compare_ids');
var_dump($ret);

$ret = array_udiff($a, $b, 'compare_names');
var_dump($ret);
?>

Which returns the following.

In the first return we see that $b has no entry in it with an id of 10.
<?
array(1) {
  [
0]=>
  array(
3) {
    [
"id"]=>
   
int(10)
    [
"name"]=>
   
string(4) "John"
   
["color"]=>
   
string(3) "red"
 
}
}
?>

In the second return we see that $a has no entry in it with an id of 15 or 40.
<?
array(2) {
  [
0]=>
  array(
3) {
    [
"id"]=>
   
int(15)
    [
"name"]=>
   
string(5) "Nancy"
   
["color"]=>
   
string(5) "black"
 
}
  [
3]=>
  array(
3) {
    [
"id"]=>
   
int(40)
    [
"name"]=>
   
string(4) "John"
   
["color"]=>
   
string(6) "orange"
 
}
}
?>

In third return we see that all names in $a are in $b (even though the entry in $b whose name is 'John' is different, the anonymous function is only comparing names).
<?
array(0) {
}
?>
up
1
grantwparks at gmail dot com
6 years ago
Re: "convoluted"

I think the point being made is that array_udiff() can be used not only for comparisons between homogenous arrays, as in your example (and definitely the most common need), but it can be used to compare heterogeneous arrays, too.

Consider:

<?php
function compr_1($a, $b) {
   
$aVal = is_array($a) ? $a['last_name'] : $a;
   
$bVal = is_array($b) ? $b['last_name'] : $b;
    return
strcasecmp($aVal, $bVal);
}

$aEmployees = array(
    array(
'last_name'  => 'Smith',
           
'first_name' => 'Joe',
           
'phone'      => '555-1000'),
    array(
'last_name'  => 'Doe',
           
'first_name' => 'John',
           
'phone'      => '555-2000'),
    array(
'last_name'  => 'Flagg',
           
'first_name' => 'Randall',
           
'phone'      => '666-1000')
    );

$aNames = array('Doe', 'Smith', 'Johnson');
   
$result = array_udiff($aEmployees, $aNames, "compr_1");

print_r($result);
?>

Allowing me to get the "employee" that's not in the name list:

Array ( [2] => Array ( [last_name] => Flagg [first_name] => Randall [phone] => 666-1000 ) )

Something interesting to note, is that the two arguments to the compare function don't correspond to array1 and array2.  That's why there has to be logic in it to handle that either of the arguments might be pointing to the more complex employee array.  (Found this out the hard way.)
up
0
jared
5 years ago
Note that php does the string conversion *before* sending the values to the callback function.
up
0
adam dot jorgensen dot za at gmail dot com
5 years ago
It is not stated, by this function also diffs array1 to itself, removing any duplicate values...
up
0
aidan at php dot net
10 years ago
This functionality is now implemented in the PEAR package PHP_Compat.

More information about using this function without upgrading your version of PHP can be found on the below link:

http://pear.php.net/package/PHP_Compat
up
-1
dmhouse at gmail dot com
9 years ago
Very easy way of achieving a case-insensitive version of array_diff (or indeed array_diff_assoc, array_intersect or any of these types of functions which have a similar function that takes a callback function as one of their parameters):

array_udiff($array1, $array2, 'strcasecmp');

This works because strcasecmp() compares two strings case-insensitively, as compared to the array_diff() which compares two strings by using the == operator, which is case-sensitive.
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