Explode string by one or more spaces or tabs

How can I explode a string by one or more spaces or tabs?
Example: A      B      C      D
 
To separate by tabs:
$comp = preg_split("/[\t]/", $var);
 
To separate by spaces/tabs/newlines:
$comp = preg_split('/\s+/', $var);
 
To seperate by spaces alone:
$comp = preg_split('/ +/', $var);