This works for symfony 1.2 and might be backwards compatible with 1.1 and 1.0, but I haven't tested it with those versions.

Place this file in an appropriate directory (eg. apps/myapp/lib/routing):

sfRegexExtendedRoute.class.php:

<?php
 
class sfRegexExtendedRoute extends sfRoute
{
  protected function compile()
  {
    $return = parent::compile();
 
    // Case-insensitive matching (default symfony behaviour = NOT case-insensitive).
    if (isset($this->options['case_sensitive']) && !$this->options['case_sensitive'])
    {
      // Make sure $this->regex is in the form "#...#[???]"
      // and that [???] does not already include "i" (the case-insensitive flag).
      if (($parts = explode('#', strrev($this->regex)))
          && 3 <= ($num_parts = count($parts))
          && '' == $parts[$num_parts-1]
          && false === strpos($parts[0], 'i'))
      {
        $this->regex .= 'i';
      }
    }
 
    return $return;
  }
}
 

Add the option case_sensitive: false in the route you want to make case-insensitive and set its class to sfRegexExtendedRoute:

apps/myapp/config/routing.yml:

...
my_route:
  url:      /my/case/insensitive/url/:whatever
  options:  { case_sensitive: false }
  class:    sfRegexExtendedRoute
...
 

Clear your cache:

> php symfony cc
 

Your url matching for that route should now be case-insensitive.

Changing case_sensitive: false to case_sensitive: true in routing.yml will revert the matching for that route back to (symfony default) case-sensitive matching.