Introduction to array_filter()

array_filter() is a powerful function in PHP. It allows you to filter elements of an array using a callable (a closure for instance). Let me guide you in using this super handy function.

Basic usage of array_filter()

array_filter() works by passing each element of an array through a callback function. If this function returns true, the element is included in the resulting array. This is particularly useful when you need to sift through data and only keep elements that meet certain conditions.

Here’s a simple example:

$array = [1, 2, 3, 4, 5];

$even = array_filter($array, fn ($value) => $value % 2 == 0);

print_r($even);

In this snippet, array_filter() retains only the even numbers from the original array.

Advanced usage of array_filter()

Beyond simple filters, array_filter() can be used in more complex scenarios. For instance, you can filter an array of objects based on the properties of those objects. It’s also possible to use it with associative arrays, filtering by key as well as value.

Common pitfalls when using array_filter()

When using array_filter(), remember that the callback function must return true or false.

$array = [1, 2, 3, 4, 5];

$even = array_filter($array, function ($value) {
    $value % 2 == 0;
});

// []
print_r($even);

If you don’t, the resulting array will be empty.

To finish this up, another common mistake is forgetting that array keys are preserved. This might lead to unexpected gaps in the numeric array indexes:

$array = [1, 2, 3, 4, 5];

$even = array_filter($array, fn ($value) => $value % 2 == 0);

// Array
// (
//     [1] => 2
//     [3] => 4
// )
print_r($even);

Did you like this article? Then, keep learning:

• Discover PHP 8.3 features including Override attribute that may relate to your code
• Get insights into PHP 8.3 updates to stay current on language improvements
• See the fastest way to check if your PHP array is empty for efficiency
• Learn about array_map(), a complementary array processing function in PHP
• Improve array sorting skills to handle arrays after filtering
• Understand how to reset array indexes after filtering with array_values()
• Learn about PHP exceptions and error handling for safer array operations
• Explore printing PHP arrays easily, helpful after filtering data for debugging
• Understand the null coalescing operator for cleaner PHP code with arrays