CODE EXAMPLE FOR PHP

mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given

// set a veariable to get your query like
$query = mysqli_query($connection-name,$sql-statment-name);

//then use an if statement to get the rows something like this
	if($query){
    	$result = mysqli_num_rows($query);     
      if($result > 0){
 // write a code for what you want to happen if the data exists in the databse
      }else{
 // write a code for what you want to happen if the data dosen't exist
     //in the databse  
      }
   }
   else{
   return "query failed";
   }
 //and thats all