title: Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, null given in
body: <p>I tried to change my mysql to mysqli. And when i do this i get error. I tried everything but i found no solution for this. </p>
  
  <p>The error that I have: (what you see is not all the errors)</p>
  
  <blockquote>
    <p>Warning: mysqli_query() expects parameter 1 to be mysqli, null given in<br>
         C:\xampp\htdocs\follow\include\database.php on line 219</p>
    
    <p>Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, null given in  C:\xampp\htdocs\follow\include\database.php on line 220</p>
    
    <p>Warning: mysqli_query() expects parameter 1 to be mysqli, null given in C:\xampp\htdocs\follow\include\database.php on line 231</p>
    
    <p>Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, null given in C:\xampp\htdocs\follow\include\database.php on line 232</p>
    
    <p>Warning: mysqli_query() expects parameter 1 to be mysqli, null given in C:\xampp\htdocs\follow\include\database.php on line 102</p>
    
    <p>... more errors</p>
  </blockquote>
  
  <p>and this is my php code</p>
  
  <pre><code>&lt;?php
  /**
   * Please subscribe to our feeds at http://blog.geotitles.com for more such tutorials
   */
  include("constants.php");
  class MySQLDB
    {
    var $connection;         //The MySQL database connection
   var $num_active_users;   //Number of active users viewing site
   var $num_active_guests;  //Number of active guests viewing site
   var $num_members;        //Number of signed-up users
   /* Note: call getNumMembers() to access $num_members! */
  
     /* Class constructor */
    function MySQLDB(){
    /* Make connection to database */
  
   $con = mysqli_connect(DB_SERVER, DB_USER, DB_PASS,DB_NAME);
  
    // Check connection
   if (mysqli_connect_errno())
       {
     echo "Failed to connect to MySQL: " . mysqli_connect_error();
      }
  
  
  
      /** 
      * Only query database to find out number of members
      * when getNumMembers() is called for the first time,
      * until then, default value set.
      */
      $this-&gt;num_members = -1;
  
      if(TRACK_VISITORS){
       /* Calculate number of users at site */
       $this-&gt;calcNumActiveUsers();
  
       /* Calculate number of guests at site */
       $this-&gt;calcNumActiveGuests();
      }
     }
  
  
     function confirmUserPass($username, $password){
     GLOBAL $con;
     /* Add slashes if necessary (for query) */
    if(!get_magic_quotes_gpc()) {
        $username = addslashes($username);
     }
  
     /* Verify that user is in database */
     $q = "SELECT password FROM ".TBL_USERS." WHERE username = '$username'";
     $result = mysqli_query($con,$q);
     if(!$result || (mysqli_num_rows($result) &lt; 1)){
       return 1; //Indicates username failure
     }
  
     /* Retrieve password from result, strip slashes */
     $dbarray = mysqli_fetch_array($result);
     $dbarray['password'] = stripslashes($dbarray['password']);
     $password = stripslashes($password);
  
    /* Validate that password is correct */
    if($password == $dbarray['password']){
       return 0; //Success! Username and password confirmed
     }
     else{
       return 2; //Indicates password failure
    }
    } 
  
  
     function confirmUserID($username, $userid){
     GLOBAL $con;
    /* Add slashes if necessary (for query) */
    if(!get_magic_quotes_gpc()) {
        $username = addslashes($username);
    }
  
    /* Verify that user is in database */
    $q = "SELECT userid FROM ".TBL_USERS." WHERE username = '$username'";
    $result = mysqli_query($con,$q);
    if(!$result || (mysqli_num_rows($result) &lt; 1)){
       return 1; //Indicates username failure
     }
  
    /* Retrieve userid from result, strip slashes */
    $dbarray = mysqli_fetch_array($result);
    $dbarray['userid'] = stripslashes($dbarray['userid']);
    $userid = stripslashes($userid);
  
    /* Validate that userid is correct */
    if($userid == $dbarray['userid']){
       return 0; //Success! Username and userid confirmed
    }
    else{
       return 2; //Indicates userid invalid
    }
    }
  
  
    function usernameTaken($username){
     GLOBAL $con;
      if(!get_magic_quotes_gpc()){
       $username = addslashes($username);
     }
    $q = "SELECT username FROM ".TBL_USERS." WHERE username = '$username'";
    $result = mysqli_query($con,$q);
    return (mysqli_numrows($result) &gt; 0);
    }
  
  
   function usernameBanned($username){ 
   GLOBAL $con;
    if(!get_magic_quotes_gpc()){
       $username = addslashes($username);
    }
    $q = "SELECT username FROM ".TBL_BANNED_USERS." WHERE username = '$username'";
    $result = mysqli_query($con,$q);
    return (mysqli_numrows($result) &gt; 0);
    }
  
  function addNewUser($username, $password, $email){
  GLOBAL $con;
    $time = time();
    /* If admin sign up, give admin user level */
    if(strcasecmp($username, ADMIN_NAME) == 0){
       $ulevel = ADMIN_LEVEL;
    }else{
       $ulevel = USER_LEVEL;
    }
    $q = "INSERT INTO ".TBL_USERS." VALUES ('$username', '$password', '0', $ulevel,     '$email', $time)";
    return mysqli_query($con,$q);
    }
  
  
   function updateUserField($username, $field, $value){
    $q = "UPDATE ".TBL_USERS." SET ".$field." = '$value' WHERE username = '$username'";
    return mysqli_query($con,$q);
  }
  
  
     function getUserInfo($username){
   GLOBAL $con;
    $q = "SELECT * FROM ".TBL_USERS." WHERE username = '$username'";
    $result = mysqli_query($con,$q);
    /* Error occurred, return given name by default */
    if(!$result || (mysqli_num_rows($result) &lt; 1)){
       return NULL;
    }
    /* Return result array */
    $dbarray = mysqli_fetch_array($result);
    return $dbarray;
    }
  
  
   function getNumMembers(){
   GLOBAL $con;
    if($this-&gt;num_members &lt; 0){
       $q = "SELECT * FROM ".TBL_USERS;
       $result = mysqli_query($con,$q);
       $this-&gt;num_members = mysqli_num_rows($result);
     }
    return $this-&gt;num_members;
    }
  
      /**
     * calcNumActiveUsers - Finds out how many active users
     * are viewing site and sets class variable accordingly.
     */
     function calcNumActiveUsers(){
   GLOBAL $con;
    /* Calculate number of users at site */
    $result = mysqli_query($con,"SELECT * FROM ".TBL_ACTIVE_USERS);
    $this-&gt;num_active_users = mysqli_num_rows($result);
       }
  
  
    function calcNumActiveGuests(){  
    GLOBAL $con;
    /* Calculate number of guests at site */
    $q = "SELECT * FROM ".TBL_ACTIVE_GUESTS;
    $result = mysqli_query($con,$q);
    $this-&gt;num_active_guests = mysqli_num_rows($result);
     }
  
  
     function addActiveUser($username, $time){
   GLOBAL $con;
    $q = "UPDATE ".TBL_USERS." SET timestamp = '$time' WHERE username = '$username'";
    mysqli_query($con,$q);
  
    if(!TRACK_VISITORS) return;
    $q = "REPLACE INTO ".TBL_ACTIVE_USERS." VALUES ('$username', '$time')";
    mysqli_query($con,$q);
    $this-&gt;calcNumActiveUsers();
     }
  
   function addActiveGuest($ip, $time){
   GLOBAL $con;
    if(!TRACK_VISITORS) return;
    $q = "REPLACE INTO ".TBL_ACTIVE_GUESTS." VALUES ('$ip', '$time')";
    mysqli_query($con,$q);
    $this-&gt;calcNumActiveGuests();
     }
  
   function removeActiveUser($username){
   GLOBAL $con;
    if(!TRACK_VISITORS) return;
    $q = "DELETE FROM ".TBL_ACTIVE_USERS." WHERE username = '$username'";
    mysqli_query($con,$q);
    $this-&gt;calcNumActiveUsers();
     }
  
  /* removeActiveGuest */
  function removeActiveGuest($ip){
  GLOBAL $con;
    if(!TRACK_VISITORS) return;
    $q = "DELETE FROM ".TBL_ACTIVE_GUESTS." WHERE ip = '$ip'";
    mysqli_query($con,$q);
    $this-&gt;calcNumActiveGuests();
  }
  
  /* removeInactiveUsers */
  function removeInactiveUsers(){
  GLOBAL $con;
    if(!TRACK_VISITORS) return;
    $timeout = time()-USER_TIMEOUT*60;
    $q = "DELETE FROM ".TBL_ACTIVE_USERS." WHERE timestamp &lt; $timeout";
    mysqli_query($con,$q);
    $this-&gt;calcNumActiveUsers();
  }
  
  /* removeInactiveGuests */
  function removeInactiveGuests(){
   GLOBAL $con;
    if(!TRACK_VISITORS) return;
    $timeout = time()-GUEST_TIMEOUT*60;
    $q = "DELETE FROM ".TBL_ACTIVE_GUESTS." WHERE timestamp &lt; $timeout";
    mysqli_query($con,$q);
    $this-&gt;calcNumActiveGuests();
  }
  
  
  function query($query){
  GLOBAL $con;
    return mysqli_query($con,$query);
  }
  };
  
  
    $database = new MySQLDB;
  
    ?&gt;
  </code></pre>