PHP router with switch statement and regular expressions not working - php

Question

I have this code in php:
$route = parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH);
switch ($route) {
case '':
echo "root";
break;
case '/':
echo "root";
break;
case (preg_match("/^[a-zA-Z0-9-_]+$/", $route) ? true : false):
echo "db";
break;
default:
header("HTTP/1.0 404 Not Found");
http_response_code(404);
print(http_response_code());
break;
}
The regexp has to match all routes containing alphanumeric characters and - and _. But it doesn't, instead all slips to the default option, 404.
Probably it is something wrong with the pregmatch inside the switch.
Please help.

Answer 1

There are few issues:
REQUEST_URI will return string with leading /, so you must add it in your regex: /^\/[a-zA-Z0-9-_]+$/
switch checks if case value matches with provided value, so you should compare it with true instead of $route:
switch (true) {
case $route == '':
...
case $route == '/':
...
case preg_match("/^\/[a-zA-Z0-9-_]+$/", $route):
...
}
But in that case it's better to use simple if conditions:
if (empty($route) || $route == '/') {
echo 'root';
return; // Use early return in order not to jump to other cases
}
if (preg_match("/^\/[a-zA-Z0-9-_]+$/", $route)) {
echo 'db';
return;
}
header("HTTP/1.0 404 Not Found");
http_response_code(404);
print(http_response_code());