I want to stress that in the user function, you do need to return either a 1 or a -1 properly; you cannot simply return 0 if the results are equal and 1 if they are not.
The following code is incorrect:
<?php
function myfunction($v1,$v2)
{
if ($v1===$v2)
{
return 0;
}
return 1;
}
$a1=array(1, 2, 4);
$a2=array(1, 3, 4);
print_r(array_uintersect($a1,$a2,"myfunction"));
?>
This code is correct:
<?php
function myfunction($v1,$v2)
{
if ($v1===$v2)
{
return 0;
}
if ($v1 > $v2) return 1;
return -1;
}
$a1=array(1, 2, 4);
$a2=array(1, 3, 4);
print_r(array_uintersect($a1,$a2,"myfunction"));
?>
array_uintersect
(PHP 5, PHP 7, PHP 8)
array_uintersect — Computes the intersection of arrays, compares data by a callback function
Description
Computes the intersection of arrays, compares data by a callback function.
Parameters
-
array -
The first array.
-
arrays -
Arrays to compare against.
-
value_compare_func -
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.
CautionReturning non-integer values from the comparison function, such as float, will result in an internal cast to int of the callback's return value. So values such as
0.99and0.1will both be cast to an integer value of0, which will compare such values as equal.CautionThe sorting callback must handle any value from any array in any order, regardless of the order they were originally provided. This is because each individual array is first sorted before being compared against other arrays. For example:
<?php
$arrayA = ["string", 1];
$arrayB = [["value" => 1]];
// $item1 and $item2 can be any of "string", 1 or ["value" => 1]
$compareFunc = static function ($item1, $item2) {
$value1 = is_string($item1) ? strlen($item1) : (is_array($item1) ? $item1["value"] : $item1);
$value2 = is_string($item2) ? strlen($item2) : (is_array($item2) ? $item2["value"] : $item2);
return $value1 <=> $value2;
};
?>
Return Values
Returns an array containing all the values of array
that are present in all the arguments.
Examples
Example #1 array_uintersect() example
<?php
$array1 = array("a" => "green", "b" => "brown", "c" => "blue", "red");
$array2 = array("a" => "GREEN", "B" => "brown", "yellow", "red");
print_r(array_uintersect($array1, $array2, "strcasecmp"));
?>The above example will output:
Array
(
[a] => green
[b] => brown
[0] => red
)
See Also
- array_intersect() - Computes the intersection of arrays
- array_intersect_assoc() - Computes the intersection of arrays with additional index check
- 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 separate callback functions
add a note
User Contributed Notes 4 notes
Nate at RuggFamily dot com ¶
17 years ago
rob dot c dot ruiz at gmail dot com ¶
6 years ago
When trying to do a case insensitive comparison between arrays of words, the strcasecmp function works very nicely with this one like so:
$arr1 = array('blue', 'green', 'red');
$arr2 = array('BLUE', 'Purple', 'Red');
$loose_matches = array_uintersect($arr1, $arr2, 'strcasecmp');
print_r($loose_matches) // array('blue', 'red');
Hayley Watson ¶
6 years ago
As for the other "compare function" callbacks, the return value from the callback function doesn't need to be -1, 0, or 1.
cmp($a,$b) just needs to be <0, =0, or >0 depending on whether $a<$b, $a=$b, or $a>$b.
Ryan C ¶
2 years ago
If you're rolling your own comparison function, keep in mind that the spaceship operator (i.e. <=>) can be your best friend. It's been around since PHP7. https://www.php.net/manual/en/language.operators.comparison.php
So, for instance, instead of a clunky function like:
<?php
function myFunction($v1, $v2) {
if ($v1 === $v2) {
return 0;
}
if ($v1 > $v2) return 1;
return -1;
}
?>
You can simplify it to:
<?php
function myFunction($v1, $v2) {
return $v1 <=> $v2;
}
?>
