The error is: Parse error: parse error, unexpected T_ENCAPSED_AND_WHITESPACE, expecting T_STRING or T_VARIABLE or T_NUM_STRING on line 44

Line 44 is
$result = mysql_query("SELECT * FROM login WHERE username= $_POST['username']");<?php

$con = mysql_connect("server","database","password");
if (!$con)
{
die("Could not connect: " . mysql_error());
}

$username = $_POST['username'];
$password = $_POST['password'];
$confirmpassword = $_POST['confirmpassword'];

$result = mysql_query("SELECT * FROM login WHERE username= $_POST['username']");

$numfound = mysql_num_rows($result);
if ($_POST['password'] != $_POST['confirmpassword'])
{
mysql_close($con);
echo "The passwords did not match";
}
else {
mysql_select_db("login", $con);
mysql_query("INSERT INTO login (username, password)
VALUES ('$username', '$password')");
echo "Thank you " . $username . ". Your account has been created.";
}
if ($numfound != 0)
{
mysql_close($con);
echo "This username is already taken.";
}
else {
mysql_select_db("login", $con);
mysql_query("INSERT INTO login (username, password)
VALUES ('$username', '$password')");
echo "Thank you " . $username . ". Your account has been created.";
}


mysql_close($con);



?>

 

Your code:
$result = mysql_query("SELECT * FROM login WHERE username= $_POST['username']");

Try:
$result = mysql_query("SELECT * FROM login WHERE username= '$_POST[username]'");

Untested, but it should work.

 

Your syntax is incorrect (does not follow mySQL recommendations)

$username = $_POST [ ' username ' ] ;
$sql = " select * from ` login ` where ` username ` = '" . $username . "'" ;
$result = mysql_query ( $sql ) ;


1. Pay attention to different: ` (reverse), ' (single quote) and " (double quote).
2. Spaces added for clarity.
3. mySQL recommends using lower cases only for keywords (unix)

Same here:
$sql2 = "insert into `login` (`username`,`password`)
values ( '" . $username . "' , '" . $password . "' ) " ;
mysql_query ($sql2);
I know, it is a lot of ` '", but it is guaranteed to work on ALL versions of mysql.