PHP如何在递归函数中计算嵌套调用的级别? [英] PHP How do I calculate level of nested calls in recursive function?

问题描述

我在php中有一个递归函数，该函数从数据库中获取文件夹树.每个文件夹都有一个ID，一个名称和一个父ID.

I have a recursive function in php which gets from a database a folder tree. Each folder has an id, a name and a parent id.

function show_subfolders($parent=0, $indent=0) {
    $indent++;
    $folders = sql_to_assoc("SELECT * FROM `folders` WHERE 'parent' = ".$parent.";");
    foreach($folders as $folder) {
        echo ' <a href="filebrowser.php?parent='.$folder['id'].'"> '.$folder['naam'].' </a><br>';
        show_subfolders($folder['id'], $indent);
    }
}

show_subfolders();

我希望变量$ indent可以告诉我们递归函数的嵌套程度，但事实并非如此，它只是计算调用次数.我希望很明显，我想知道每个子元素的代".

I expect that the variable $indent tells us the level of nestedness of the recursive function, but it is not.. it just counts the number of calls. I hope it is clear that I want to know the 'generation' of each child-element.

推荐答案

尝试将$ indent var置于函数范围之外，此外，在结束遍历节点(文件夹)的内容之后，您将返回一个级别，以便在某些时候，您应该使用$ indent-;

Try taking the $indent var outside of the function scope, also, after you end traversing a node(folder) contents, you are going back up a level so at some point you should do a $indent--;

$indent = 0;

function show_subfolders(){
    // give this function access to $indent
    //you could also use a class var $this->indent if you make this into a class method
    global $indent;

    $folders = sql_to_assoc("SELECT * FROM `folders` WHERE 'parent' = ".$parent.";");
    foreach($folders as $folder) {
        echo str_repeat ('&nbsp;', $indent).' <a href="filebrowser.php?parent='.$folder['id'].'"> '.$folder['naam'].' </a><br>';
        $indent++;
        show_subfolders($folder['id']);
        $indent--;
    }
}

还添加了str_repeat函数，以便在浏览器中呈现链接时缩进"链接.尽管更好的方法是在中绘制链接，这将允许您使用CSS控制视觉缩进.那会做到的:

Also added the str_repeat function so that your links are 'indented' when rendered in the browser. Although a better approach would be to draw the links in a which will allow you to control the visual indentation with css. That would make it:

$indent = 0;

function show_subfolders(){
    // give this function access to $indent
    //you could also use a class var $this->indent if you make this into a class method
    global $indent;

    $folders = sql_to_assoc("SELECT * FROM `folders` WHERE 'parent' = ".$parent.";");
    if (count($folders)){
        echo '<ul>';
        foreach($folders as $folder) {
            echo '<li><a href="filebrowser.php?parent='.$folder['id'].'"> '.$folder['naam'].' </a></li>';
            $indent++;
            show_subfolders($folder['id']);
            $indent--;
        }
        echo '</ul>';
    }
}

这篇关于PHP如何在递归函数中计算嵌套调用的级别?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！