PHP Exercises: Group the elements of an array based on the given function

PHP: Exercise-83 with Solution

Write a PHP program to group the elements of an array based on the given function.

Sample Solution:

PHP Code:

<?php
// License: https://bit.ly/2CFA5XY

// Function definition for 'groupBy' that takes an array of items and a grouping function as parameters
function groupBy($items, $func)
{
    // Initialize an empty associative array to store the grouped items
    $group = [];

    // Iterate through each item in the array
    foreach ($items as $item) {
        // Check if the grouping function is a callable function or a valid function name
        if ((!is_string($func) && is_callable($func)) || function_exists($func)) {
            // If callable, use 'call_user_func' to get the key and group the item
            $key = call_user_func($func, $item);
            $group[$key][] = $item;
        } 
        // Check if the item is an object
        elseif (is_object($item)) {
            // If an object, use the property specified by the grouping function as the key and group the item
            $group[$item->{$func}][] = $item;
        } 
        // Check if the item has a key specified by the grouping function
        elseif (isset($item[$func])) {
            // If set, use the specified key as the grouping key and group the item
            $group[$item[$func]][] = $item;
        }
    }

    // Return the associative array containing the grouped items
    return $group;
}

// Call 'groupBy' with an array of strings and a grouping function based on string length, then display the result using 'print_r'
print_r(groupBy(['one', 'two', 'three', 'four'], 'strlen'));

?>

Sample Output:

Array
(
    [3] => Array
        (
            [0] => one
            [1] => two
        )

    [5] => Array
        (
            [0] => three
        )

    [4] => Array
        (
            [0] => four
        )

)

Flowchart:

PHP Code Editor:

Have another way to solve this solution? Contribute your code (and comments) through Disqus.

Previous: Write a PHP program to get the index of the last element for which the given function returns a truth value.
Next: Write a PHP program to check a flat list for duplicate values. Returns true if duplicate values exists and false if values are all unique.