错误 php 和我的意外T_IS_EQUAL

代码是：

<?php
require_once('connection.php');
// Check $username and $password 
/*
if(empty($_POST['username']))
{
    echo "UserName/Password is empty!";
    return false;
}
if(empty($_POST['password']))
{
    echo "Password is empty!";
    return false;
}
*/
// Define $username and $password 
$username=$_POST['username']; 
$password=md5($_POST['pass']);
// To protect MySQL injection (more detail about MySQL injection)
$username1 = stripslashes($username);
$password2 = stripslashes($password);
$username3 = mysql_real_escape_string($username);
$password4 = mysql_real_escape_string($password);
$sql="SELECT * FROM $WebsiteUsers WHERE username='$username' and password='$password'";
$result=mysql_query($sql);
// If result matched $username and $password, table row must be 1 row
if( mysql_num_rows($result) ==1){ //get num of rows
    $row = mysql_fetch_assoc($result);
    if ($password4) == $row['password']
    {
        session_register("username");
        session_register("password"); 
        echo "Login Successful";
        return true;
    }
    else {
        echo "Wrong Username or Password";
        return false;
    }
}
else{
    echo "Wrong Username or Password";
    return false;
}
?>

错误一直说：

解析错误：语法错误，第 36 行/home/u771046626/public_html/IP/check-user.php 中的意外T_IS_EQUAL

我看了一下，找不到我的错误，所以我希望这里的人们可以。