How can I get parameters from a URL string?

You can use the parse_url() and parse_str() for that.

$parts = parse_url($url);
parse_str($parts['query'], $query);
echo $query['email'];

If you want to get the $url dynamically with PHP, take a look at this question:

Get the full URL in PHP

All the parameters after ? can be accessed using $_GET array. So,

echo $_GET['email'];

will extract the emails from urls.

Use the parse_url() and parse_str() methods. parse_url() will parse a URL string into an associative array of its parts. Since you only want a single part of the URL, you can use a shortcut to return a string value with just the part you want. Next, parse_str() will create variables for each of the parameters in the query string. I don't like polluting the current context, so providing a second parameter puts all the variables into an associative array.

$url = "https://mysite.com/test/[email protected]&testin=123";
$query_str = parse_url($url, PHP_URL_QUERY);
parse_str($query_str, $query_params);
print_r($query_params);

//Output: Array ( [email] => [email protected] [testin] => 123 )