//To clear array you are able to simply re-instantiate it
$foo = array();
//To clear $foo from the symbol table use
unset($foo);
$colors = array("red","","blue",NULL);
$colorsNoEmptyOrNull = array_filter($colors, function($v){
return !is_null($v) && $v !== '';
});
//$colorsNoEmptyOrNull is now ["red","blue"]
$emptyArray = [];
$emptyArray = array();
$emptyArray = (array) null;
$emptyArray = [];
$emptyArray = array();
$emptyArray = (array) null;
$my_array = array_fill(0, $size_of_the_array, $some_data);
unset($foo); // $foo is gone
$foo = array(); // $foo is here again