logical operators in php

                                              logical operators in php :  && , || , !




<?php


$a=10;
$b=20;
if($a<15 && $b>15)
echo  "$a is less than 15 and $b is grater than 15";


?>
output : 10 is less than 15 and 20 is grater than 15






<?php


$a=10;
$b=20;
if($a<15 || $b<15)
echo  "$a is less than 15 and $b is grater than 15";


?>
output : 10 is less than 15 or 20 is grater than 15





<?php


$a=10;
$b=20;
if(!($a<15 && $b>15))
echo  "$a is less than 15 and $b is grater than 15";


?>
output : 


nothing to display , because , inner value is true and we apply ! to that so , the value of if statement is false