CODEWITHSUNDEEP
phparraysusort
EstSiim
EstSiim

Reputation: 441

PHP usort inside foreach order alphabetically

I am trying to figure out why my code wont work as i expect. I have an array:

$persons = array(
    0 => array(
        'person' => 'John',
        'children' => array('Eve', 'Mark', 'Alto')
    ),
    1 => array(
        'person' => 'Susy',
        'children' => array('Ruby', 'Adam', 'Tõnu')
    )
);

Loop the array and sort childrens alphabetically

foreach( $persons as $person ) {

    usort($person['children'], function( $a, $b ) {
        return strcmp( $a, $b );
    });
    var_dump($person['children']); //shows children array items alphabetically ordered

}

But after foreach chidrens are still in starting order

var_dump($persons); //shows that children names are not ordered alphabetically

Thank you for your time

Upvotes: 1

Views: 2936

Answers (1)

Matt S
Matt S

Reputation: 15374

The foreach loop is creating what is effectively a copy of the array value inside the loop. The copy is sorted but not altering the original array. To do so you can make it a reference with &:

foreach ($persons as &$person) {

From the documentation:

On each iteration, the value of the current element is assigned to $value and the internal array pointer is advanced by one... In order to be able to directly modify array elements within the loop precede $value with &. In that case the value will be assigned by reference.

Another way to reference the arrays directly is to iterate over the indexes and reference the elements:

for ($i = 0; $i < count($persons); $i++) {
    usort($persons[$i]['children']), function($a, $b) {
        return strcmp($a, $b);
    });
}

Upvotes: 2

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