PHP Exercises: Filter the collection using the given callback

Last update on April 19 2025 11:50:18 (UTC/GMT +8 hours)

89. Filter Collection Using a Callback Function

Write a PHP program to filter the collection using the given callback.

Sample Solution:

PHP Code:

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

// Function definition for 'reject' that takes an array of items and a filtering function as parameters
function reject($items, $func)
{
    // Use 'array_filter' to filter the items based on the given function
    // Use 'array_diff' to get the items that are not present in the filtered array
    // Use 'array_values' to reindex the resulting array
    return array_values(array_diff($items, array_filter($items, $func)));
}

// Call 'reject' with an array and an anonymous function filtering items with a length greater than 4, then display the result using 'print_r'
print_r(reject(['Green', 'Red', 'Black', 'White'], function ($item) {
    return strlen($item) > 4;
}));

?>

Explanation:

Function Definition:

The function reject is defined to take two parameters:

$items: an array of items to be filtered.
$func: a filtering function that determines which items to reject.

Filtering Items:

Inside the function:

array_filter($items, $func) is used to create an array of items that pass the condition specified in $func.
This array contains only the items for which the filtering function returns true.

Getting Rejected Items:

array_diff($items, array_filter($items, $func)) is then used to find the items in the original array ($items) that are not present in the filtered array.
This effectively gives the items that do not satisfy the condition defined by the filtering function.

Reindexing the Array:

array_values(...) is applied to the result of array_diff to reindex the resulting array, ensuring that the keys are reset in the output.

Return Statement:

The modified array, containing only the rejected items, is returned from the function.

Function Call:

The reject function is called with an array of color names (['Green', 'Red', 'Black', 'White']) and an anonymous function that filters out items with a length greater than 4.

Displaying Results:

The result of the reject function call is displayed using print_r, showing the array of items that do not satisfy the condition (in this case, items with length 4 or less).

Purpose:

The reject function effectively filters out items from an array based on a specified condition, returning only those items that do not meet the condition defined by the filtering function.

Output:

Array
(
    [0] => Red
)

Flowchart:

For more Practice: Solve these Related Problems:

Write a PHP script to apply a custom callback function to filter an array and output the resulting subset.
Write a PHP function to retain elements of an array where the callback returns true.
Write a PHP script to demonstrate filtering of a collection with a user-defined predicate function.
Write a PHP script to remove elements that do not pass a given callback test and output the filtered array.

PHP Code Editor:

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