Filtering array with array_intersect() - values are equal as integers, but not as strings

Question

If I've got an array of values that are basically zero-padded string representations of various numbers and another array of integers, will array_intersect() still match elements of different types?

For example, would this work:

$arrayOne = array('0003', '0004', '0005');
$arrayTwo = array(4, 5, 6);

$intersect = array_intersect($arrayOne, $arrayTwo);

// $intersect would then be = "array(4, 5)"

And if not, what would be the most efficient way to accomplish this? Just loop through and compare, or loop through and convert everything to integers and run array_intersect() after?

Community · Accepted Answer · 2023-11-17 19:59:20Z

4

From https://www.php.net/manual/en/function.array-intersect.php:

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

In your example, $intersect will be an empty array because 5 !== "005" and 4 !== "004"

edited Nov 17, 2023 at 19:59

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answered Nov 3, 2008 at 18:14

Davide Gualano

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1 Comment

steven Over a year ago

And I think it should be mentioned that (string)"5" === (string)5.

Zak · Accepted Answer · 2008-11-03 18:13:49Z

3

$ cat > test.php

<?php
$arrayOne = array('0003', '0004', '0005');
$arrayTwo = array(4, 5, 6);

$intersect = array_intersect($arrayOne, $arrayTwo);

print_r($intersect );

?>

$ php test.php

Array ( )

$

So no, it will not. But if you add

foreach($arrayOne as $key => $value)
{
   $arrayOne[$key] = intval($value);
}

you will get

$ php test.php

Array ( [1] => 4 [2] => 5 )

answered Nov 3, 2008 at 18:13

Zak

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1 Comment

user2589071 Over a year ago

Doesn't work when i test it.function matched_ids() { $cart_ids = array_merge( wp_list_pluck(WC()->cart->get_cart_contents(), 'variation_id'), wp_list_pluck(WC()->cart->get_cart_contents(), 'product_id') ); $product_ids = get_option('restricted_product_ids'); $ids = explode( ' ', $product_ids ); foreach( $product_ids as $key => $value ) { $product_ids[$key] = intval($value); return array_intersect( $product_ids[$key], $cart_ids ); } }

mickmackusa · Accepted Answer · 2023-11-23 11:13:02Z

It is true that array_intersect() performs loose comparisons, but your zero-padded strings will not be evaluated as loosely equal when the integers are coerced to numeric strings.

This does not mean that you will need to abandon the native array intersect family of functions. array_uintersect() is a very appropriate tool and, by casting the parameters as int type, will require no iterated function calls to suitably compare the values.

Code: (Demo)

var_export(
    array_uintersect(
        $arrayOne,
        $arrayTwo,
        fn(int $a, int $b) => $a <=> $b
    )
);
// array (1 => '0004', 2 => '0005',)

Or swap the order of the input arrays: (Demo)

var_export(
    array_uintersect(
        $arrayTwo,
        $arrayOne,
        fn(int $a, int $b) => $a <=> $b
    )
);
// array (0 => 4, 1 => 5,)

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