<?
//if the following words seperated by 2 continuous TAB char
$line="This             is              a               test";
$token=strtok($line,"\t\t");
while($token){
  echo "$token<br>";
  $token=strtok("\t\t");
}
?> 
expecting result should be:
This
is
a
test
but it's not.
Though there is other solution to this problem still,
str_replace \t\t -> \t 
or using explode