minor #4343 Compiled PHP for customized route matching (GeertDD)

This PR was submitted for the master branch but it was merged into the 2.4 branch instead (closes #4343).

Discussion
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Compiled PHP for customized route matching

The second parameter of `rtrim()` is a character mask. By checking if `rtrim($pathinfo, '/contact') === ''`, `$pathinfo` could be any URL containing those characters and not only "/contact" which was configured as the route path, for example:

    $pathinfo = '/octocat';
    var_dump(rtrim($pathinfo, '/contact') === ''); // bool(true)

Commits
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fb5e820 Compiled PHP for customized route matching

Author: wouterj

book/routing.rst

@@ -833,7 +833,7 @@ variables that are passed into the expression:
     Behind the scenes, expressions are compiled down to raw PHP. Our example
     would generate the following PHP in the cache directory::
 
-        if (rtrim($pathinfo, '/contact') === '' && (
+        if (0 === strpos($pathinfo, '/contact') && (
             in_array($context->getMethod(), array(0 => "GET", 1 => "HEAD"))
             && preg_match("/firefox/i", $request->headers->get("User-Agent"))
         )) {