[PHP] Filter an array

Question

I have an array like this:

$categories_array = array(
[0] => 'category_1',
[1] => 'category_2',
[2] => 'category_3',
[3] => 'category_4'
)

I'd like to "filter" the array to get a new one. For example, I'd like to have a new array with only 'category_2' and 'category_3' like this:

$new_categories_array = array(
[1] => 'category_2',
[2] => 'category_3',
)

How can I accomplish this result?

Answer 1

unset($new_categories_array[0]);
unset($new_categories_array[3]);

..might do the trick

Answer 2

Use preg_grep:

$new_categories_array = preg_grep('/category_[23]/', $categories_array);

Answer 3

See

• array_diff — Computes the difference of arrays
• array_intersect — Computes the intersection of arrays

Example:

$original = array('category_1','category_2','category_3','category_4');
$new      = array_diff($original, array('category_1', 'category_4'));

print_r($new);

Output:

Array
(
    [1] => category_2
    [2] => category_3
)

When using array_intersect the returned array would contain cat 1 and 4 obviously.

Answer 4

While I agree preg_grep is a good solution in your example, if you want a more general case function, look at array_filter - http://ca.php.net/manual/en/function.array-filter.php