php - Testing if a Select Query found results -

hi i'm new php , appreciate if tell me i'm going wrong in code. put code in context, i'm using facebook authenticate users , adding signup details app database. in following code intend check if user exists in database , if not add them. reason can't test $result

i've checked query variables , echo out without problem

@ $con = new mysqli('localhost', 'username', 'password', 'database'); if(mysqli_connect_errno()){     echo 'error: not connect database. please try again later';     exit; }  $query = "select * users oauth_provider = 'facebook' , oauth_uid ='".$uid."'";  $result = $con->query($query);   if($result === false){     $insertquery = "insert ('oauth_provider', 'oauth_uid', 'username') values ('facebook', '".$uid."', '".$username."')";     $result = $con->query($query); } 

i should add have code working using older mysql approach. have read better use object-oriented mysqli approach.

here's old working code

if($session){ $con = mysql_connect('localhost', 'user', 'password'); $select_db = mysql_select_db('database');  if(!$con || !$select_db){     die('could not connect: ' . mysql_error()); } else{     echo "connected database , table selected"; }  $query = mysql_query("select * users oauth_provider = 'facebook' , oauth_uid = ". $user['id']); $result = mysql_fetch_array($query);  if(empty($result)){     $query = mysql_query("insert users (oauth_provider, oauth_uid, username) values ('facebook', {$user['id']}, '{$user['name']}')");     $query = mysql_query("select * users id = " . mysql_insert_id());     $result = mysql_fetch_array($query); }  } 

any can give me appreciated.

if( $result instanceof mysqli_result && $result->num_rows==0) 

break down:

$result instanceof mysqli_result 

this ensure query go through , results return

$result->num_rows==0 

this check previous query matching existing records