Php 通过递归调用函数从数据库检索数据后动态填充菜单

我正在为我的大学项目建立一个网站，并决定创建首页。在它上面，我试图通过表示父类别来显示菜单，并通过递归调用一个函数（该函数通过从数据库获取数据来执行相同操作）来动态填充类别及其子类别。但是，结果仅显示主菜单或父菜单，而不显示子类别。我不知所措。 php代码如下所示

<?php
session_start();
include("connection.php");
$a=0;
if(isset($_SESSION["valid_user"]))
{
    echo "WELCOME ";
    echo $_SESSION["valid_user"];

    $name = $_SESSION["valid_user"];

    $sqllist   = "select * from category order by category_name";
    $rscatlist = mysql_query($sqllist);

    $catid1 = "";
    $opt    = "";

    while($rowcatlist = mysql_fetch_array($rscatlist))
    {
        $catid1  = $rowcatlist["category_id"];
        $catname = $rowcatlist["category_name"];
        $opt .= "<option value='$catid1'>$catname</option>";    
    }

    $sql1 = "select * from register where email_id='$name'" ;
    $rs1  = mysql_query($sql1);
    $row  = 0;
    $row1 = "";

    while($row1=mysql_fetch_array($rs1))
    {
        $row = $row1["admin"];
    }

    if($row==1)
    {
        echo "&nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp<a href='admin/usermanagement/index.php'>Management Services </a> &nbsp ";
    }
    echo "<p align='right'><a href='logout.php'><font size='3'>logout</font></a></p>"."<br>" ."<br/>";
}
else
{
    echo "<p align='right'><a href='register.php'><font size='3'>Register</font></a> or <a href='login.php'><font size='3'>Login</font></a></p>"."<br/>"."<br/>";
}

$tbl = "";

$cat_id = 0;
$tbl = recursive($tbl,$cat_id);

function recursive($tbl,$cat_id)
{
    $sql = "select * from category where parent_id='$cat_id'";
    $rs  = mysql_query($sql);
    $tbl.="<ul>";
    while($row=mysql_fetch_array($rs))
    {
        $tbl .= "<li><a href='product.php?category_id=$row'[category_id]'>$row[category_name]</a>";
        $sql1 = "select * from category where parent_id=$row'[category_id]'";
        $rs1  = mysql_query($sql1);

        while($row1 = mysql_fetch_array($rs1))
        {  
            recursive($tbl,$row["category_id"]);
        }

        $tbl.="</li>";
    }  
    $tbl.="</ul>";
    return $tbl;
}


?>

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在定义递归函数之前调用该函数似乎很奇怪。同样奇怪的是，您只为$cat_id 0调用该函数。您是否也需要遍历所有的主级别类别ID并将它们传递到函数中

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天哪，有没有人教过你评论你的代码

谢谢你指出这一点。很抱歉，因为我已经有一段时间没有以用户身份登录stackoverflow，所以延迟回复。这确实是问题所在。是的，评论和我从来没有很好地相处过；