stop explode（）期望参数2是字符串警告

Question

I have a form that's allow the user to select 2 or more categories.

php check url like:

 $categories= (!isset($_GET["categories"])?0:explode(";",$_GET["categories"]));

normal URL is like this

    site.com/cat.php?page=&categories=1;2

if the user change the URL to

    site.com/cat.php?page=&categories[1]

the site will show

      Warning: explode() expects parameter 2 to be string, array given in...

so I tried to check $_GET like this

     is_string($_GET["category"])

but with no luck

Answer 1

Try this?

$catString=is_string($_GET["categories"]) ? $_GET["categories"] : implode(';',$_GET["categories"]);

$categories = (!isset($_GET["categories"])?0:explode(";",$catString));

or I guess a better solution would be (instead of converting from array to string and back to array which is kinda silly):

$categories = (!isset($_GET["categories"])? "" : $_GET["categories"];

$categories = is_array($categories) ? $_GET["categories"] : explode(";",$catString));