PHP Cookbook

4.6. Changing Array Size

Problem

You want to modify the size of an array, either by making it larger or smaller than its current size.

Solution

Use array_pad( ) to make an array grow:

// start at three
$array = array('apple', 'banana', 'coconut');

// grow to five
$array = array_pad($array, 5, '');

Now, count($array) is 5, and the last two elements contain the empty string.

To reduce an array, you can use array_splice( ):

// no assignment to $array
array_splice($array, 2);

This removes all but the first two elements from $array.

Discussion

Arrays aren’t a predeclared size in PHP, so you can resize them on the fly.

To pad an array, use array_pad( ). The first argument is the array to be padded. The next argument is the size and direction you want to pad. To pad to the right, use a positive integer; to pad to the left, use a negative one. The third argument is the value to be assigned to the newly created entries. The function returns a modified array and doesn’t alter the original.

Here are some examples:

// make a four-element array with 'dates' to the right
$array = array('apple', 'banana', 'coconut');
$array = array_pad($array, 4, 'dates');
print_r($array);
Array
               (
                   [0] => apple
                   [1] => banana
                   [2] => coconut
                   [3] => dates
               )

// make a six-element array with 'zucchinis' to the left
$array = array_pad($array, -6, 'zucchini');
print_r($array);
Array
               (
                   [0] => zucchini
                   [1] => zucchini
                   [2] => apple
                   [3] => banana
                   [4] => coconut
                   [5] => dates
               )

Be careful. array_pad($array, 4, 'dates') makes sure ...