PHP Array Exercises : Filter array elements with certain key-names

Last update on May 30 2022 11:50:05 (UTC/GMT +8 hours)

PHP Array: Exercise-51 with Solution

Write a PHP program to filter out some array elements with certain key-names.

Sample Solution:

PHP Code:

<?php
$first_array = array('c1' => 'Red', 'c2' => 'Green', 'c3' => 'White', 'c4' => 'Black'); 
$second_array = array('c2', 'c4');
$result = array_diff_key( $first_array, array_flip( $second_array));
print_r($result);
?>

Sample Output:

Array                                                       
(                                                           
    [c1] => Red                                             
    [c3] => White                                           
)

Flowchart:

PHP Code Editor:

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Previous: Write a PHP script to get the last value of an array without affecting the pointer.
Next: Write a PHP function to filter a multi-dimensional array. The function will return those items that will match with the specified value.

What is the difficulty level of this exercise?

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PHP: Tips of the Day

How to Sort Multi-dimensional Array by Value?

Try a usort, If you are still on PHP 5.2 or earlier, you'll have to define a sorting function first:

Example:

function sortByOrder($a, $b) {
    return $a['order'] - $b['order'];
}

usort($myArray, 'sortByOrder');

Starting in PHP 5.3, you can use an anonymous function:

usort($myArray, function($a, $b) {
    return $a['order'] - $b['order'];
});

And finally with PHP 7 you can use the spaceship operator:

usort($myArray, function($a, $b) {
    return $a['order'] <=> $b['order'];
});

To extend this to multi-dimensional sorting, reference the second/third sorting elements if the first is zero - best explained below. You can also use this for sorting on sub-elements.

usort($myArray, function($a, $b) {
    $retval = $a['order'] <=> $b['order'];
    if ($retval == 0) {
        $retval = $a['suborder'] <=> $b['suborder'];
        if ($retval == 0) {
            $retval = $a['details']['subsuborder'] <=> $b['details']['subsuborder'];
        }
    }
    return $retval;
});

If you need to retain key associations, use uasort() - see comparison of array sorting functions in the manual

Ref : https://bit.ly/3i77vCC