curl options constants have duplicated INTEGER values

I'm running PHP 5.2.9-1 for Windows and am seeing something that strikes me rather odd in the curl setopt constants, collisions of sorts I guess you might call them. The sample script below says it all ... $curl = get_defined_constants(true); $curl = $curl['curl']; foreach($curl as $k => $v) { if (strpos($k, 'CURLOPT_', 0) === false) { unset($curl[$k]); } } print count($curl) . "\n"; print_r($curl); /** 2 dupes, 10009 and 10026 [CURLOPT_READDATA] => 10009 [CURLOPT_INFILE] => 10009 [CURLOPT_SSLKEYPASSWD] => 10026 [CURLOPT_SSLCERTPASSWD] => 10026 */ I'm retrieving just the CURLOPT_* constants and was not expecting to see duplicate integer values here. CURLOPT_READDATA is not documented in the online manual. I can read into that value somewhat and assume that either constant (CURLOPT_READDATA or CURLOPT_INFILE) might suggest that the value supplied should be "The file that the transfer should be read from when uploading" However, the SSL constants don't make sense. I don't see how they could be "interchangeable" like the first set. Anybody have any further insight?