Array Intersect giving wrong output

Question

I need to find common elements between two arrays. My code is:

$sql="SELECT DISTINCT fk_paytbl_discounts_discountid as discountid from paytbl_discounts_students WHERE fk_vtiger_cf_601='".$categoryid."'";
$discountstudentinfo=$objdb->customQuery($sql,false);

$sql1="SELECT DISTINCT fk_paytbl_discounts_discountid as discountid from paytbl_discounts_variants WHERE fk_vtiger_products_productid='".$variantid."'";
$discountvariantinfo=$objdb->customQuery($sql1,false);

$commondiscount=array_intersect($discountvariantinfo,$discountstudentinfo);

First array

Array
(
    [0] => Array
        (
            [discountid] => 2
        )

    [1] => Array
        (
            [discountid] => 8
        )

    [2] => Array
        (
            [discountid] => 5
        )

    [3] => Array
        (
            [discountid] => 4
        )

)

Second array

Array
(
    [0] => Array
        (
            [discountid] => 1
        )

    [1] => Array
        (
            [discountid] => 5
        )

)

Common array

Array
(
    [0] => Array
        (
            [discountid] => 1
        )

    [1] => Array
        (
            [discountid] => 5
        )

)

Common array should have only discountid 5 but its showing 1 also.

Please help me on this

Thanks

erisco · Accepted Answer · 2010-05-14 06:49:59Z

http://php.net/array_intersect

Note: Two elements are considered equal if and only if (string) $elem1 === (string) $elem2. In words: when the string representation is the same.

So the reason you are experiencing a problem is because, for example:

(string) array('discountid' => 5) == (string) array('discountid' => 8)

If you are running PHP 5.3, this is one solution:

$comparisonFunction = function($elem1, $elem2) {
    return $elem1['discountid'] == $elem2['discountid'];
}
$commondiscount = array_uintersect(
    $discountvariantinfo,
    $discountstudentinfo,
    $comparisonFunction
);

Prior to PHP 5.3 you could use the uglier create_function() instead of the nifty closure. If your executing inside a method it would likely be easy to tack on a new private method to use as a callback.

If you are not using PHP 5.3 and you really don't want to use a callback, you could use the following idea:

$uniqueDiscounts = array();
foreach ($discountvariantinfo as $dvi) {
    $uniqueDiscounts[$dvi['discountid']] += 1;
}
foreach ($discountstudentinfo as $dsi) {
    $uniqueDiscounts[$dsi['discountid']] += 1;
}

$commondiscount = array();
foreach ($uniqueDiscounts as $ud => $count) {
    if ($count == 2) {
        $commondiscount[] = array('discountid' => $ud);
    }
}

You will, of course, want to tidy this up or add comments to explain the algorithm.

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