Limit multidimensional array to X arrays inside - php

Question

I have a multidimentional array like this:
$my_array = array(
array($user_id, $id, $type, $log, $url, $timestamp),
array($user_id, $id, $type, $log, $url, $timestamp),
array($user_id, $id, $type, $log, $url, $timestamp),
// and so on...
);
$my_array has a random amount of arrays inside. I want to limit the amount of arrays to 5 inside $my_array. How can I achieve this? So, if there are 5 arrays inside, and one more is added, then remove the last array...

Answer 1

Just use a function to add arrays to it, then do your checks. E.g
function addToArray($arr, $newValue, $limit=5) {
if (count($arr) >= $limit) {
array_shift($arr);
}
$arr[] = $newValue;
return $arr;
}
The function array_shift removes the first element and returns the shortened array.
If it is possible for things to be added to the array outside of this function, you can generalize:
function addToArray($arr, $newValue, $limit=5) {
while (count($arr) >= $limit) {
array_shift($arr);
}
$arr[] = $newValue;
return $arr;
}
EDIT: Added improvements suggested by Jonathan Kuhn.

Answer 2

Add the new value and then call array_slice.
If you want to add to the end of the array:
//array with more than 5
$array = range(1, 8); // [1, 2, 3, 4, 5, 6, 7, 8]
//add the element
$array[] = 9;
//get the last 5
$array = array_slice($array, -5);
//output: [5, 6, 7, 8, 9]
http://codepad.viper-7.com/DL91ZK
If you want to add to the beginning of the array
//array with more than 5
$array = range(1, 8); // [1, 2, 3, 4, 5, 6, 7, 8]
//add to the array
array_unshift($array, 0);
//get the first 5
$array = array_slice($array, 0, 5);
//output: [0, 1, 2, 3, 4]
http://codepad.viper-7.com/RGfohJ