基于使用 php 类的先前下拉列表的下拉列表

Question

我的页面中有以下下拉菜单

<label for="state">State: </label>
<select name="state" class="dropdown">
<option value="" selected>Please Select</option>
<?php echo $states->getStates(); ?>
</select>

下拉菜单本身可以正常工作，并且可以自行填充状态。但是现在我希望它能够选择一个州，并根据该州的城市下拉菜单显示该州的相应城市。

下面是我的课程。我只是不知道如何调用 myclass 的 getCity 函数并将状态下拉列表中的选定值传递给它。

states.php

class states{
function getStates(){
        $success = false;
        try{
            $con = new PDO( DB_DSN, DB_USERNAME, DB_PASSWORD ); 
            $con->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
            $sql = "SELECT DISTINCT(state) FROM tbl_zip ORDER BY state ASC";

            $stmt = $con->prepare( $sql );
            $stmt->execute();


            $valid = $stmt->fetchAll();

            if( $valid ) {
                $success = true;
                    $list = "";
                    // Loop through list of states
                    foreach($valid as $row) {
                        $list .= '<option value=\"' . $row["state"] .'\">' . $row["state"] . '</option>';
                    }   

            }


            $con = null;
            return $list;
         }catch (PDOException $e) {
             echo $e->getMessage();
             return $success;
         }
    }

    function getCity($state){
        $success = false;
        try{
            $con = new PDO( DB_DSN, DB_USERNAME, DB_PASSWORD ); 
            $con->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
            $sql = "SELECT DISTINCT city FROM tbl_zip WHERE state = :state ORDER BY city ASC";

            $stmt = $con->prepare( $sql );
            $stmt->bindValue( "state", $state , PDO::PARAM_STR );
            $stmt->execute();


            $valid = $stmt->fetchAll();

            if( $valid ) {
                $success = true;
                    $list = '<select name=\"state\">';
                    $list .= '<option value=\"\" selected>Please Select</option>';
                    // Loop through list of states
                    foreach($valid as $row) {
                        $list .= '<option value=\"' . $row["city"] .'\">' . $row["city"] . '</option>';
                    }   
                    $list .= '</select>';
            }


            $con = null;
            return $list;
         }catch (PDOException $e) {
             echo $e->getMessage();
             return $success;
         }
    }                                               
}

Answer 1

不确定，到底是什么让你烦恼，但是这个怎么样：

$city = $states->getCity($_POST['state']);