The stream context options on Horde_Http_Request_Fopen and curl 
options on Horde_Http_Request_Curl options are inaccessible.  There 
are no seams to modify them without creating a new class, copy/pasting 
the oversized send() method and apply customization within.  This 
leads to unnecessary work the next time you try to upgrade the 
underlying Horde libs.

The quickest solution is to extract the initialization of $opts and 
$curl into a protected method.  This would allow deveopers to extend 
the class, overwrite the method, and add or modify options before 
returning the value to send() for usage.

If publishing protected methods like this in a public project is not 
desirable you could possibly create an options Builder (meaning 
Builder Pattern) which could be injected.  The Builder could have 
methods like setProxy($host, $port), setAuth($scheme, $username, 
$password), and of course a build()/make()/create() method that 
returns the assembled object.  The Builder could be extended by 
developers to add more options at any stage of the building process.