PHP has a vast collection of functions that make developers’ lives easier by reducing the complexity of their code. One such function is array_filter(). It is a built-in function that takes an array as an input and filters its elements based on a user-defined callback function.
Syntax
The syntax of array_filter() is as follows:
array_filter(array $array, callable $callback = null, int $flag = 0): array
array: The input array that needs to be filtered.callback: An optional parameter that defines the filter function to be applied to each element. If no callback function is provided, all the empty elements in the array will be removed.flag: An optional parameter that specifies the behavior of the function. By default, it has a value of 0, which means that the callback function will only be applied to the elements that have a truthy value.array: The output array containing the filtered elements.
Examples
Example 1: Filter Even Numbers
The following example demonstrates how to filter even numbers from an array:
$numbers = array(1, 2, 3, 4, 5, 6);
$even_numbers = array_filter($numbers, function($number) {
return $number % 2 == 0;
});
print_r($even_numbers);The output of the above code will be:
Array
(
[1] => 2
[3] => 4
[5] => 6
)As you can see, the output array contains only the even numbers 2, 4, and 6.
Example 2: Remove Empty and Null Values
The following example demonstrates how to remove empty and null values from an array:
$fruits = array('apple', 'banana', '', 'orange', null, 'kiwi');
$filtered_fruits = array_filter($fruits);
print_r($filtered_fruits);The output of the above code will be:
Array
(
[0] => apple
[1] => banana
[3] => orange
[5] => kiwi
)As you can see, the empty and null values (”, null) have been removed from the array.
Example 3: Filter by Key
You can also use array_filter() to filter an array by its keys, rather than its values. Here’s an example:
$prices = array(
'apple' => 0.99,
'banana' => 0.25,
'orange' => 0.50,
'kiwi' => 1.50,
);
$filtered_prices = array_filter($prices, function($key) {
return ($key !== 'banana' && $key !== 'kiwi');
}, ARRAY_FILTER_USE_KEY);
print_r($filtered_prices);This will output:
Array
(
[apple] => 0.99
[orange] => 0.5
)In this example, we’ve filtered out the ‘banana’ and ‘kiwi’ keys from the $prices array by returning false from the callback function for those keys.
Example 4: Filter Multidimensional Arrays
The array_filter() function can also be used to filter multidimensional arrays. Here’s an example:
$products = array(
array('name' => 'Apple', 'category' => 'fruit', 'price' => 0.99),
array('name' => 'Banana', 'category' => 'fruit', 'price' => 0.25),
array('name' => 'Orange', 'category' => 'fruit', 'price' => 0.50),
array('name' => 'Milk', 'category' => 'dairy', 'price' => 2.50),
array('name' => 'Cheese', 'category' => 'dairy', 'price' => 3.50),
array('name' => 'Bread', 'category' => 'grains', 'price' => 1.50),
);
$filtered_products = array_filter($products, function($product) {
return ($product['category'] === 'fruit' && $product['price'] < 1.00);
});
print_r($filtered_products);This will output:
Array
(
[0] => Array
(
[name] => Apple
[category] => fruit
[price] => 0.99
)
[1] => Array
(
[name] => Banana
[category] => fruit
[price] => 0.25
)
[2] => Array
(
[name] => Orange
[category] => fruit
[price] => 0.5
)
)In this example, we’ve filtered out all products that don’t have a category of ‘fruit’ or a price of less than 1.00.
Conclusion
array_filter() is a powerful function in PHP that can be used to filter arrays based on a variety of criteria. It can be used to remove empty or null values, filter elements based on a custom callback function, or even filter multidimensional arrays. By using this function, you can significantly reduce the complexity of your code and make it more efficient. I hope this article has given you a good understanding of how array_filter() works and how it can be used in your PHP projects.
Thanks for reading!
