apparently, sscanf always splits at spaces, even if spaces are not specified in the format. consider this script:
<?php
$str = "This is a\tsentence with\ttabs";
$scanned = sscanf($str, "%s\t%s\t%s");
echo join(" : ", $scanned);
?>

this echoes "This : is : a", not the expected "This is a : sentence with : tabs."
this behaviour is fine if your strings don't contain spaces, but if they do you'd be better off using explode().