POST not working Notice Undefined index username

Question

Possible Duplicate    PHP     Notice  Undefined variable     and    Notice  Undefined index          So  I am currently learning PHP and was reading on a book about the md5 function for passwords  so I decided to give it a try and see how it goes  I also decided to use the POST method rather than the GET  since I saw people saying that it is safer and doesn t let the variables appearing on the URL   For my testing project I made a very simple form  which follows    lt  DOCTYPE html gt   lt html gt       lt head gt           lt meta http-equiv  Content-Type  content  text html  charset UTF-8  gt           lt title gt  lt  title gt       lt  head gt       lt body gt           lt form action  dologin  method  POST  gt               lt table border  0  gt                   lt tbody gt                       lt tr gt                           lt td gt Username  lt  td gt                           lt td gt  lt input type  text  name  username  gt  lt  td gt                       lt  tr gt                       lt tr gt                           lt td gt Password  lt  td gt                           lt td gt  lt input type  password  name  password  gt  lt  td gt                       lt  tr gt                   lt  tbody gt               lt  table gt               lt input type  submit  value  Login  gt           lt  form gt       lt  body gt   lt  html gt    The problem is that when I enter the values on BOTH fields and click  Login  I get the following output on the other PHP file   Notice  Undefined index  username in C  xampp htdocs md5 home dologin index php on line 11 Username non existent   Here follows the code for the   dologin index php  file   lt  DOCTYPE html gt   lt html gt       lt head gt           lt meta http-equiv  Content-Type  content  text html  charset UTF-8  gt           lt title gt  lt  title gt       lt  head gt       lt body gt           lt  php             mysql connect  localhost    root   or die mysql error                 mysql select db  test   or die mysql error                  query    SELECT password FROM users WHERE username      POST  username                     result   mysql query  query                row   mysql num rows  result               if isset  row                     password    mysql result  result  row - 1                     enteredpassword   md5  w         GET  password      3f                       if  password     enteredpassword                       if  isset   COOKIE  PHPSESSID                              session start                                                SERVER  LOGIN STATUS     true                    else                       die  Access denied                                        else                   die  Username non existent                             gt       lt  body gt   lt  html gt    Any help at all on my issue is very much appreciated  thank you for reading

User · Accepted Answer

undefined index means that somewhere in the   POST array  there isn t an index  key  for the key username    You should be setting your posted values into variables for a more clean solution  and it s a good habit to get into    If I was having a similar error  I d do something like this    username     POST  username       you should really do some more logic to see if it s set first echo  username    If username didn t turn up  that d mean I was screwing up somewhere  You can also   var dump   POST     To see what you re posting  var dump is really useful as far as debugging  Check it out  var dump

User · Answer

You should check if the POST  username   is defined  Use this above    username        if isset   POST  username           username     POST  username        SELECT password FROM users WHERE username     username

User · Answer

first of all   be sure that there is a post  if isset   POST  username               check if the username has been set     second  and most importantly  sanitize the data  meaning that   query    SELECT password FROM users WHERE username      POST  username          is deadly dangerous  instead use   query    SELECT password FROM users WHERE username    mysql real escape string   POST  username           and please research the subject sql injection

[php] $_POST not working. "Notice: Undefined index: username..."

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