Why doesn't array_filter() mutate my strings while it iterates?

Question

So I have the following array:

array:3 [
  0 => "6.05"
  1 => "5.94"
  2 => "5.96"
]

Which is passed through the following function:

$filteredShots = array_filter($shots, function($shot) {
        if (is_numeric($shot)) {
            return floatval($shot);
        }
});

Which then spits out, the exact same array:

array:3 [
  0 => "6.05"
  1 => "5.94"
  2 => "5.96"
]

Why are these still strings? I told it to convert them to floatval. Am I doing something wrong? Am I crazy?

If I die and dump on the return statement I get: 6.05, not "6.05" so ... why is the array reflecting that?

AbraCadaver · Accepted Answer · 2018-07-11 18:24:50Z

1

array_filter expects true or false from the callback function to retain or remove the corresponding element. In your implementation, unless you have a 0 or falsey value it will always return true. You want array_map that actually applies the return of the callback:

$filteredShots = array_map(function($shot) {
        if (is_numeric($shot)) {
            return floatval($shot);
        }
}, $shots);

You can also modify the original array using array_walk:

array_walk($shots, function(&$shot) {
        if (is_numeric($shot)) {
            $shot = floatval($shot);
        }
});

You can use array_filter to remove non-numeric:

$filteredShots = array_filter($shots, function($shot) {
        return is_numeric($shot) ? true : false;
});
//or simply
$filteredShots = array_filter($shots, 'is_numeric');

edited Jul 11, 2018 at 18:24

answered Jul 11, 2018 at 18:08

AbraCadaver

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1 Comment

Barmar Over a year ago

@TheWebs That's what documentation is for, although the function names seem to describe what they do pretty clearly. Filtering means to reduce a collection to just the items that match some criteria.

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