How do i use array_filter() on a mapped array(array_map()) in php?

Question

In the following code I have two arrays $x and $m. I then mapped the two arrays as $k but what I want is that after the two arrays are mapped, if there is an empty element on either of the array $x and $m ($x in this case) then it needs to filter out the corresponding mapped elements from $k as well which is the mapped array.

<!DOCTYPE html>
<html>
<body>
<?php  
$x = array("apple", "", 2, null, -5, "orange", 10, false, "",22);
var_dump(array_filter($x));
echo "<br/>";
$m = [12,13,14,15,16,17,18,19,20,21];

$k = array_map(null, $x, $m);
array_filter($k);
shuffle($k);

$count = 1;
foreach ($k as $a) { 
if($count <= 8){  
echo "The number is: $a[0]. $a[1]. <br>";
 }else{
 break;
 }
   $count++; 
}
?>  
</body>
</html>

But this doesn't seem to work. The output I get is the following:

array(6) { [0]=> string(5) "apple" [2]=> int(2) [4]=> int(-5) [5]=> string(6) "orange" [6]=> int(10) [9]=> int(22) } 
The number is: . 19.
The number is: -5. 16.
The number is: apple. 12.
The number is: 22. 21.
The number is: . 20.
The number is: . 15.
The number is: . 13.
The number is: 2. 14.

What I want is that . 20 or . 15 etc be filtered out. How do I go about solving this?

array_filter returns a new, filtered array. It doesn't modify the original array. Use it akin to array_map, not akin to shuffle. — deceze
– deceze ♦, Commented Oct 13, 2020 at 11:37

u_mulder · Accepted Answer · 2020-10-13 11:51:17Z

1

As noticed in comments - array_filter does not modify the array, instead - it returns new array, so your code can be rewritten as:

<?php  
$x = array("apple", "", 2, null, -5, "orange", 10, false, "",22);
$filteredX = array_filter($x);

var_dump($filteredX);

echo "<br/>";

$m = [12,13,14,15,16,17,18,19,20,21];

$k = array_map(null, $filteredX, $m);
$filteredK = array_filter($k);
shuffle($filteredK);

$count = 1;
foreach ($filteredK as $a) { 
if($count <= 8){  
echo "The number is: $a[0]. $a[1]. <br>";
 }else{
 break;
 }
   $count++; 
}
?>

But! As array_map with null callback returns array of arrays, array_filter does not filter elements that have both elements not empty.

What shows print_r($k) (excerpt):

Array
(
    [0] => Array
        (
            [0] => apple
            [1] => 12
        )

    [1] => Array
        (
            [0] => 2
            [1] => 13
        )

    [2] => Array
        (
            [0] => -5
            [1] => 14
        )

    [3] => Array
        (
            [0] => orange
            [1] => 15
        )

    [4] => Array
        (
            [0] => 10
            [1] => 16
        )

    [5] => Array
        (
            [0] => 22
            [1] => 17
        )

    [6] => Array
        (
            [0] => 
            [1] => 18
        )

    [7] => Array
        (
            [0] => 
            [1] => 19
        )

As you can see, elements under indices 6,7 and more have empty value under key [0]. As array_filter filters only plain values, to clear your array from subarrays with empty first element, you should use array_filter with a callback:

$k = array_map(null, $filteredX, $m);
$filteredK = array_filter($k, function($v) { return isset($v[0], $v[1]);});
shuffle($filteredK);

After this filtering you will not get empty values. Final fiddle here.

answered Oct 13, 2020 at 11:51

u_mulder

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4 Comments

Mahim Enterprises Over a year ago

But once you filter out the array with empty values $x here, that implies that the filtered array will map to the none filtered one $m in this case. When I run this code for example what I also got is that 2 from $x is mapped to 13 from $m which is not what i want. I want both 2 and empty string from $m be filtered out. Not one of them be mapped to the other element

u_mulder Over a year ago

Sorry, I don't get what you mean.

Mahim Enterprises Over a year ago

I meant when I open the final fiddle of the code, I get -5 from array $x matched with 14 from array $m in the output. But according to the original array i want -5 from array $x to match with 16 from array $m. In the solution you gave $filteredX = array_filter($x); is done in the very beginning. That will filter the array and then map it.

u_mulder Over a year ago

So, don't use first array_filter then.

Roman · Accepted Answer · 2020-10-13 11:51:57Z

0

    $x = array("apple", "", 2, null, -5, "orange", 10, false, "",22);
    array_filter($x);
    echo "<br/>";
    $m = [12,13,14,15,16,17,18,19,20,21];

    $k = array_map(null, $x, $m);

    /* This is the filter code */
    $k = array_filter($k, function($value) {
        return (bool) $value[0] && (bool) $value[1];
    });
    /***************************/

    shuffle($k);

    $count = 1;
    foreach ($k as $a) {
        if($count <= 8){
            echo "The number is: $a[0]. $a[1]. <br>";
        }else{
            break;
        }
        $count++;
    }

answered Oct 13, 2020 at 11:51

Roman

3301 silver badge9 bronze badges

3 Comments

Roman Over a year ago

You're welcome! I hope you understand how it works, please vote for my answer, thank you!

Mahim Enterprises Over a year ago

Hey, yeah i think i understood the code. Thanks again.

Roman Over a year ago

Great, please mark the answer as correct for this question, thanks.

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