Question

Im trying to come up with MySQL logic for a search function I got on my page. Its a simple form where the user can choose to fill in search criteria. The criteria(s) is send as arguments to a function that generates the mysql logic. This is whats inside the PHP controller file:

   case 'search':
         if((empty($_POST['username'])) && (empty($_POST['firstname'])) && (empty($_POST['lastname']))
                && (empty($_POSt['agemin'])) && (empty($_POST['agemax'])) && (empty($_POST['country']))){
                $members = get_all_username();
         } else {
            if(isset($_POST['username'])){
                $otheruser = $_POST['username'];
            } else { $otheruser = null; }
            if(isset($_POST['agemin'])){
                $ageMin = $_POST['agemin'];
            } else { $ageMin = null; }
            if(isset($_POST['agemax'])){
                $ageMax = $_POST['agemax'];
            } else { $ageMax = null; }
            if(isset($_POST['country'])){
                $country = $_POST['country'];
            } else { $country = null; }
            //if(isset($_POST['isonline']))

        $members = search_members($otheruser, $ageMin, $ageMax, $country);
        }
        include('displaySearch.php');
        break;

So if nothing is set a complete list of all the members is generated and displayed. This is the function that is called if any of the inputs is set:

function search_members($username, $ageMin, $ageMax, $country){
    global $db;
    $query = "SELECT username FROM profiles WHERE username = :username 
        AND age > :ageMin AND age < :ageMax AND country = :country";
    $statement = $db->prepare($query);
    $statement->bindValue(':username', $username); $statement->bindValue(':ageMin', $ageMin);
    $statement->bindValue(':ageMax', $ageMax); $statement->bindValue(':country', $country);
    $statement->execute();
    if($statement->rowCount() >= 1){
        return $statement->fetchAll();
    } else {
        return false;
    }
}

The mysql logic is obviously wrong. I need a set of conditions (in the MySQL logic if possible) that checks the PHP variables for value and if there is none it should not be accounted for when querying the database. So if only the username is set in the form the other variables should not be included in the SQL logic.

I’ve looked up the MySQL IF() condition but Im still not able to come up with proper code that does what I need. If someone could point me in the right direction I would be able to do the rest myself. Any other approach for solving this kind of problem is also welcome.

Answer 1

If i understand your problem, then the simple way is to use if else to build sql query, for example

$sql = "SELECT username FROM profiles WHERE 1 "
if (!is_null($username)) {
    $sql .= " AND username = :username ";
}
// All other checks