title: PHP Convert mysql to mysqli
body: <p>The following script works fine:</p>
  
  <pre><code>$host="localhost"; // Host name 
  $username=""; // Mysql username 
  $password=""; // Mysql password 
  $db_name="test"; // Database name 
  $tbl_name="members"; // Table name 
  
  // Connect to server and select databse.
  mysql_connect("$host", "$username", "$password")or die("cannot connect"); 
  mysql_select_db("$db_name")or die("cannot select DB");
  
  // username and password sent from form 
  $myusername=$_POST['myusername']; 
  $mypassword=$_POST['mypassword']; 
  
  // To protect MySQL injection (more detail about MySQL injection)
  $myusername = stripslashes($myusername);
  $mypassword = stripslashes($mypassword);
  $myusername = mysql_real_escape_string($myusername);
  $mypassword = mysql_real_escape_string($mypassword);
  $sql="SELECT * FROM $tbl_name WHERE username='$myusername' and password='$mypassword'";
  $result=mysql_query($sql);
  
  // Mysql_num_row is counting table row
  $count=mysql_num_rows($result);
  
  // If result matched $myusername and $mypassword, table row must be 1 row
  if($count==1){
  
  // Register $myusername, $mypassword and redirect to file "login_success.php"
  session_register("myusername");
  session_register("mypassword"); 
  header("location:login_success.php");
  }
  else {
  echo "Wrong Username or Password";
  }
  </code></pre>
  
  <p>Why, when I replace only the mysql_connect and mysql_select_db statements (keeping everything else including all passwords the same) with the following, do i get the "Wrong Username or Password" echo?</p>
  
  <pre><code>mysqli_connect($host,$username,$password,$db_name) or die("cannot connect");
  </code></pre>