<?php $a=1; $b=2; $c=3; if($a<$b<$c) { echo 'success'; } else echo "failure"; ?> what would be output of this php script ?

You won't have any output but a syntax error.

To compare three variables in php, you must to isolate each condition like this :

`if (($a < $b) < $c)` instead of  `if ($a < $b < $c)`

and you'll have success as output.

success 

because :b>a

and b<c