将url参数添加到带有分隔逗号问题的$ _GET变量中

Question

This is my function, I simply want to output a link like this:

www.example.com/new?cat=22,23,27

If a category value already exists I want to delete it. If it doesn't exist yet, i want to add it.

This is my function:

function setorunset($value) {
    if(isset($_GET['cat'])) { //wenn schon eine categorie da ist
        if(strpos($value,$_GET['cat']) === false ) { 
            $_GET['cat'] .= ",".$value; }
        else {
            str_replace(",".$value, ",", $_GET['cat']);
        }
        echo http_build_query($_GET);   
    }
    else {
        echo http_build_query($_GET).'&cat='.$value;
    }
}

I simply can't find the error why this shouldnt work: I call this function with: setorunset(22);

Does anyone find any error?

Answer 1

Don't use strpos() for this. If you have cat=101,11 and you call setorunset(10) it will match the 10 in 101.

Instead, use explode() to create an array from the value, update the array, and then use implode() to create the new value.

function setorunset($value) {
    if(isset($_GET['cat'])) { //wenn schon eine categorie da ist
        $cat = explode(',', $_GET['cat']);
        $pos = array_search($value, $cat);
        if ($pos === false) {
            $cat[] = $value;
        } else {
            unset($cat[$pos]);
        }
        $_GET['cat'] = implode(',', $cat);
    }
    else {
        $_GET['cat'] = $value;
    }
    echo http_build_query($_GET);
}