[OSM-dev] API - modifying tags?

[OJW]

Reply to myself here (because I might want to know this stuff in future), it 
was the age-old "Expect: 100-continue" problem.

Apparently some HTTP libraries just add this expectation header (with varied 
spellings of 'continue') to your PUT headers unless you find a way to 
suppress them.

The server responds with "417: Expect failed" (probably before it even reaches 
the OSM API, which is why it's not listed in our page of response codes, 
although maybe we should put a note about it there)

In CURL (using PHP code here) the way to fix it was:

curl_setopt($ch,CURLOPT_HTTPHEADER, array("Expect:"));

i.e. explicitly set the header to blank


Useful debugging methods for CURL are:

(1) Display the full server response
	curl_setopt($ch, CURLOPT_HEADER, true);

(2) Log the verbose output somewhere
    curl_setopt($ch, CURLOPT_VERBOSE, true);
    curl_setopt($ch, CURLOPT_STDERR, $someFilePointer);





That's HTTP response 417 CURL PHP Expect 100 continue expect failed for the 
benefit of search engines indexing this list...