如何修复代码中的Undefined变量？

Question

                if($generator == "" || $_SESSION['rank'] == 5){
                    $generatorquery = "SELECT * FROM `generators`";
                }else{
                    $generatorquery = "SELECT * FROM `generators` WHERE `id` = ".$generator;
                }

如何修复第一行代码？

Answer 1

如果我说得对，如果你想检查变量“generator”是否为空（它有一个值）那么这对你有用：

 if(empty($generator) || $_SESSION['rank'] == 5)