I recently installed pdftk using instruction provided at stack overflow

I installed it, and run the commanded whereis pdftk the result was

/usr/local/bin/pdftk    /usr/bin/pdftk 

I have the powerpannel access and I saw it through it that pdftk actually exists at the location

i run the command pdftk --version, it was okay

but when in php i use

<?php
$command = "pdftk --help";
system("PATH=/usr/local/bin/ && $command",$response);
if ($response===FALSE){
   echo 'sorry error occured';
}
else{
    echo $response;
}

?> 

the output is 127 the version i am using is 1.41 and the output '127' is something that i cant understand

can somebody guide me?