You want to modify the size of an array, either by making it larger or smaller than itscurrent size.
Use array_pad() to make an array grow:
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// 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, $array[3] and $array[4], contain the empty string.
To reduce an array, you can use array_splice():
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// no assignment to $array array_splice($array, 2); |
This removes all but the first two elements from $array.
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:
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// 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 an $array is at least four elements long; it doesn’t add four new elements.
In this case, if $array was already four elements or larger, array_pad() would return an unaltered $array.
Also, if you declare a value for a fourth element, $array[4]:
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$array = array('apple', 'banana', 'coconut'); $array[4] = 'dates'; print_r($array); |
you end up with a four-element array with indexes 0, 1, 2, and 4:
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Array ( [0] => apple [1] => banana [2] => coconut [4] => dates ) |
PHP essentially turns this into an associative array that happens to have integer keys. The array_splice() function, unlike array_pad(), has the side effect of modifying the original array.
It returns the spliced-out array. That’s why you don’t assign the return value to $array. However, like array_pad(), you can splice from either the right or left.
So calling array_splice() with a value of -2 chops off the last two elements from the end:
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// make a four-element array $array = array('apple', 'banana', 'coconut', 'dates'); // shrink to three elements array_splice($array, 3); // remove last element, equivalent to array_pop() array_splice($array, -1); // only remaining fruits are apple and banana print_r($array); |
