过滤结果的正确方法是什么？到目前为止，我得到的是一个表格，你可以输入名字，姓氏，电话和其他的东西。如何使语句忽略空输入字段而不是搜索空值？
我用的是事先准备好的语句，当我过滤我用的东西时 WHERE firstname = ? and lastname = ? 如果某个东西是空的，则条件改变语句。我怎样才能避免在有条件的情况下发表成百上千的声明？

$stmt = $this->mysqli->prepare("SELECT * FROM cust");

    if(!empty($firstname) && !empty($lastname)) {
        $stmt = $this->mysqli->prepare("SELECT * FROM cust WHERE as_first = ? AND as_last = ?");
        $stmt->bind_param("ss", $firstname, $lastname);
    } else if(!empty($firstname) && empty($lastname)) {
        $stmt = $this->mysqli->prepare("SELECT * FROM cust WHERE as_first = ?");
        $stmt->bind_param("s", $firstname);
    } else if(empty($firstname) && !empty($lastname)) {
        $stmt = $this->mysqli->prepare("SELECT * FROM cust WHERE as_last = ?");
        $stmt->bind_param("s", $lastname);
    }