How can I make the $validation false, I tried this but it will never return false to me.
if (isset($_POST['submit'])) {
    // starting date post data
    $startDay = $_POST['startDay'];
    $startMonth = $_POST['startMonth'];
    $startYear = $_POST['startYear'];
    // ending date post data
    $endDay = $_POST['endDay'];
    $endMonth = $_POST['endMonth'];
    $endYear = $_POST['endYear'];
    // team post data
    $team = $_POST['selectTeam'];
    $validation = true;
    if ($validation) {
        if (!isset($startDay) || $startDay === 'defaultDay') {
            $validation = false;
        }
        if (!isset($startMonth) || $startMonth === 'defaultMonth') {
            $validation = false;
        }
        if (!isset($startYear) || $startYear === 'defaultYear') {   
            $validation = false;
        }
        if (!isset($endDay) || $endDay === 'defaultDay') {
            $validation = false;
        }
        if (!isset($endMonth) || $endMonth === 'defaultMonth') {
            $validation = false;
        }
        if (!isset($endYear) || $endYear === 'defaultYear') {
            $validation = false;
        }
        if (!isset($team) || $team === 'defaultTeam') {
            $validation = false;
        }
        if ($validation=true) {
            echo 'testing';
        } elseif ($validation=false) {
            echo 'false';
        }
    }
}
 
     
    