html form - matching login info to external file php -

i have html registration form username , password inputs. usernames , passwords stored in .txt file this:

username1,password1   username2,password2 

i need match entered username , password stored ones. code, not working, can advise?

<form action = "./get_form.php" method = "post" name = "form" >      username:     <input type= "text" name = "username" >     password:     <input type= "text" name = "passwords" >     remember me:     <input type= "checkbox" name = "remember" value = "checked" >     <input type = "submit" name = "submit" value= "submit query" >   </form>   <?php  $username= $_post["username"]; $password= $_post["password"]; $contents = file("passwords.txt"); $found = false;  foreach ($contents $line) {     $data = explode(',', $line);         if (($username === $data[0]) && ($password === $data[1])) {         $found = true;     } } ?>