PHP array_merge if not empty - php

Question

Trying to merge 4 arrays, but some may be empty at certain times.
$array_1 = array('something1', something2);
$array_2 = array('something3', something4);
$array_3 = array();
$array_4 = array('something1', something2);
$list = array_merge($array_1,$array_2,$array_3,$array_4);
print_r($list);
But if one of the arrays are empty, there will be an error.
I've been googling forever, but I can't find a solid simple answer on how to check for empty arrays before merging.
Argument #2 is not an array
Or whichever array is empty is the argument number. How do I strip out empty arrays before merging?

Answer 1

There is NO error with an empty array. There is only an error if the arg is NOT an array.
You could check is_array() or:
$list = array_merge(
(array)$array_1,
(array)$array_2,
(array)$array_3,
(array)$array_4
);

Answer 2

Okay here you go, this should do the trick (if you make array of the initial arrays):
$arrs = array();
$arrs[] = array('something1', something2);
$arrs[] = array('something3', something4);
$arrs[] = array();
$arrs[] = array('something1', something2);
$list = array();
foreach($arrs as $arr) {
if(is_array($arr)) {
$list = array_merge($list, $arr);
}
}
print_r($list);

Answer 3

Array merge supports empty array()
Doc:
Example #3 Simple array_merge() example
http://us1.php.net/array_merge
<?php
$array1 = array();
$array2 = array(1 => "data");
$result = array_merge($array1, $array2);
?>
Result
Array
(
[0] => data
)
You are getting notice because something2, something4 should be quoted as string or $ as variable.
PHP Notice: Use of undefined constant something2 - assumed 'something2'