Deleting From MySQL Database Using PHP

[Akenatehm]

Hey Guys,

 

I need to reverse this script so that it has the opposite effect and deletes the user instead of adding them. I need it to be able to search through the database when you input either of the fields (username, email etc.) or all of them etc. Help would be greatly appreciated. Here is my code:

 

<?php

include "../connect.php";

if(isset($_POST['submit']))

{

   $username=$_POST['username'];

   $password=$_POST['password'];
   
   $email=$_POST['email'];

   if(strlen($username)<1)

   {

      print "You did not enter a username.";

   }

   else if(strlen($password)<1)

   {

      print "You did not enter a password.";

   }

   else

   {

      $insert="Insert into users (username,pass,email) values('$username','$password','$email')";

      mysql_query($insert) or die("Could not insert comment" . mysql_error());
  
  print "User Added. <A href''<a href="home.html">Click here</a> To Go Home.";
   }

  }

?>

 

Thanks in Advanced

Akenatehm

[Mchl]

And what problems do you have with doing it?

[Akenatehm]

I am completely unsure of how to do this. As far as I know it would involve

 

delete from

 

somewhere but I am not sure how I would go about this whole thing.

[Mchl]

Yes.

The query would look like

 

DELETE FROM users WHERE username = $username OR email = $email

 

I think it won't be difficult for you to modify the code now.

[Akenatehm]

Thanks.

[Mchl]

Be careful. It will not ask you for any confirmation. And you should also protect yourself against SQL injecitons.

 

Just think what happens if someone enters username to be deleted as this:

 

$username = "'a' OR 1=1 "

 

(the query would look like this

DELETE FROM users WHERE username = 'a' OR 1=1 OR email = $email

 

which would delete all users)

[Akenatehm]

I am not very sure about what this script is doing.

 

I understand that $username is the variable but I am not unsure about what the 'a' is, is it the id of the html form? and the 1=1, I am also unsure of that.

 

 $username = "'a' OR 1=1 " 

 

 

[peranha]

I am not very sure about what this script is doing.

 

I understand that $username is the variable but I am not unsure about what the 'a' is, is it the id of the html form? and the 1=1, I am also unsure of that.

 

 $username = "'a' OR 1=1 " 

 

 

 

the "'a' OR 1=1 "  is a sort of hack, if you dont clean your variables before you use them, people can get all sorts of information from your database, in this case, they would delete all your data.

 

Look up "SQL injections" in google, and it will tell you about it.

[Akenatehm]

Thanks for that. I had a look and I understand it now. Much appreciated.