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Accepted
Oskar Calvo
Asked: 2020-05-31 05:43:17 +0800 CST 2020-05-31 05:43:17 +0800 CST

Condition inside an array_map closure returns values ​​of more

  • 772

I have this array:

<?php 
$array = [
    '0' => ['asset' => 'wadus'],
    '1' => ['asset' => 'wadus2'],
    '2' => ['asset' => ''],
];
?>

The var_dumpone with the array returns me:

array(3) {
    [0] =>
    array(1) {
        'asset' =>
        string(5) "wadus"
    }
    [1] =>
    array(1) {
        'asset' =>
        string(6) "wadus2"
    }
    [2] =>
    array(1) {
        'asset' =>
        string(0) ""
    }
}

If I iterate with foreachI can discriminate empty elements.

$clean_assets = [];

foreach ($array as $asset) {
    if(!empty($asset['asset'])) {
        $clean_assets[] = $asset['asset'];
    } 
}

The one var_dumpreturns $clean_assetsme:

array(2) {
    [0] =>
    string(5) "wadus"
    [1] =>
    string(6) "wadus2"
}

If I use a closure:

$clean_assets = array_map(function($asset) {
    if(!empty($asset['asset'])){
        return $asset['asset'];
    }    
}, $array);

It returns me this:

array(3) {
    [0] =>
    array(1) {
        'asset' =>
        string(5) "wadus"
    }
    [1] =>
    array(1) {
        'asset' =>
        string(6) "wadus2"
    }
    [2] =>
    array(1) {
        'asset' =>
        string(0) ""
    }
}

Does anyone know why the anonymous function has this behavior?

php

2 Answers

  1. Best Answer

    I really don't know how the second response can come out like this (applying the closure) since applying your methods to me appears as follows:

    array(3) {
  [0]=>
  string(5) "wadus"
  [1]=>
  string(6) "wadus2"
  [2]=>
  NULL
}

    Searching a bit in the documentation of the function array_mapI found the following:

    The returned array will retain the keys of the array argument if and only if exactly one array is passed . If more than one array is passed, the returned array will have sequential keys of type integer.

    Therefore, from the previous paragraph it can be deduced that if you pass a single array as an argument, it will retain its structure.

    I have done a second test to verify that this was true with a different condition:

    $clean_assets = array_map(function($asset) {
    if($asset['asset'] == "wadus2"){
       return $asset['asset'];
    }    
}, $array);

    With the corresponding answer:

    array(3) {
  [0]=>
  NULL
  [1]=>
  string(6) "wadus2"
  [2]=>
  NULL
}

    Conclusion : By singleing arraythe closure and using the function array_map, it will maintain the structure of the original array by padding only the values ​​that match the condition and leaving the rest of the values ​​NULL.

    • 3

  2. I have an error in the approach, the function , if the callbackarray_filter is not passed to it, returns an array in which the empty elements are eliminated.

    Example #2 : array_filter()without callback :

    <?php
$entrada = array(
    0 => 'foo',
    1 => false,
    2 => -1,
    3 => null,
    4 => ''
);
print_r(array_filter($entrada));
?>

    The result of the example would be:

    Array
(
    [0] => foo
    [2] => -1
)

    Example source: PHP:array_filter

    • 0