How to Change Date from dd/mm/yyyy to yyyy-dd-mm in PHP

$date_array = explode("/",$date); // split the array
$var_day = $date_array[0]; //day seqment
$var_month = $date_array[1]; //month segment
$var_year = $date_array[2]; //year segment
$new_date_format = "$var_year-$var_day-$var_month"; // join them together

/**
 * @param string $date (d.m.y, y-m-d, y/m/d)
 * @return string|bol
 */

function convertDate($date) {
       // EN-Date to GE-Date
       if (strstr($date, "-") || strstr($date, "/"))   {
               $date = preg_split("/[\/]|[-]+/", $date);
               $date = $date[2].".".$date[1].".".$date[0];
               return $date;
       }
       // GE-Date to EN-Date
       else if (strstr($date, ".")) {
               $date = preg_split("[.]", $date);
               $date = $date[2]."-".$date[1]."-".$date[0];
               return $date;
       }
       return false;
}