php - 从数据库中加载值以根据上一个下拉菜单中的选择创建下拉菜单

Question

我的问题是我尝试根据先前下拉列表中的选择加载下拉列表。我正在从数据库中加载值。但是当我使用 $_get['emirate'] 时，我没有得到值。它说该值未设置。

$data = mysql_query("SELECT * FROM emirate") 
        or die(mysql_error()); 

    Print "<table border cellpadding=3>"; 
    print"<tr><th><form method=get action='index.php'><select id=EMIRATE size=1><OPTION value=all>all</option>";
    while($info = mysql_fetch_array( $data )) 
    { 
        Print "<option value=". $info['em_name'] .">".$info['em_name']."</option>"; 
    }
    print"</select></form></th>";
    if(isset($_GET['EMIRATE'])){
        $name=$_GET['EMIRATE'];
        echo $name;

        $data = mysql_query("SELECT a_name FROM areas where em_id=(select em_id from emirate where em_name=\"".$name."\")") 
        or die(mysql_error());
        Print "<th><select name=AREAS size=1>";
        while($info = mysql_fetch_array( $data ))
        {
            Print "<option >".$info['a_name']."</option>";
        }
        print"</select></th>";
    }

Answer 1

我发现了问题。

I haven't put a submit button and hence my form wasn't getting submitted. And hence I wasn't getting any value from $_GET.

http://php.net/manual/en/reserved.variables.get.php

现在顺利拿到结果了。