RESTful API methods HEAD OPTIONS

Question

I m writing a RESTful API module for an application in PHP  and I m a bit mixed on the verbs HEAD and OPTIONS         OPTIONS   Used to retrieve the available HTTP verbs for a given resource    HEAD     Used to determine whether a given resource is available       If someone could clarify  these verbs  that would be much appreciated     The clarification was with respect to RESTful API architectures re-purposing HTTP verbs  I ve since come to the realization that both HEAD and OPTIONS should not be re-purposed  and instead behave predictably as any HTTP application should  Oh  how we grow in 2 years

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OPTIONS method returns info about API  methods content type   HEAD method returns info about resource  version length type   Server response  OPTIONS  HTTP 1 1 200 OK Allow  GET HEAD POST OPTIONS TRACE Content-Type  text html  charset UTF-8 Date  Wed  08 May 2013 10 24 43 GMT Content-Length  0   HEAD  HTTP 1 1 200 OK Accept-Ranges  bytes Content-Type  text html  charset UTF-8 Date  Wed  08 May 2013 10 12 29 GMT ETag   780602-4f6-4db31b2978ec0  Last-Modified  Thu  25 Apr 2013 16 13 23 GMT Content-Length  1270         OPTIONS Identifying which HTTP methods a resource supports  e g  can we DELETE it or update it via a PUT    HEAD Checking whether a resource has changed  This is useful when maintaining a cached version of a resource    HEAD Retrieving metadata about the resource  e g  its media type or its size  before making a possibly costly retrieval   HEAD  OPTIONS Testing whether a resource exists and is accessible  For example  validating user-submitted links in an application       Here is nice and concise article about how HEAD and OPTIONS fit into RESTful architecture

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OPTIONS tells you things such as  What methods are allowed for this resource    HEAD gets the HTTP header you would get if you made a GET request  but without the body  This lets the client determine caching information  what content-type would be returned  what status code would be returned  The availability is only a small part of it

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As per   http   www w3 org Protocols rfc2616 rfc2616-sec9 html  9 2 OPTIONS The OPTIONS method represents a request for information about the communication options available on the request response chain identified by the Request-URI  This method allows the client to determine the options and or requirements associated with a resource  or the capabilities of a server  without implying a resource action or initiating a resource retrieval  Responses to this method are not cacheable  If the OPTIONS request includes an entity-body  as indicated by the presence of Content-Length or Transfer-Encoding   then the media type MUST be indicated by a Content-Type field  Although this specification does not define any use for such a body  future extensions to HTTP might use the OPTIONS body to make more detailed queries on the server  A server that does not support such an extension MAY discard the request body  If the Request-URI is an asterisk   quot   quot    the OPTIONS request is intended to apply to the server in general rather than to a specific resource  Since a server s communication options typically depend on the resource  the  quot   quot  request is only useful as a  quot ping quot  or  quot no-op quot  type of method  it does nothing beyond allowing the client to test the capabilities of the server  For example  this can be used to test a proxy for HTTP 1 1 compliance  or lack thereof   If the Request-URI is not an asterisk  the OPTIONS request applies only to the options that are available when communicating with that resource  A 200 response SHOULD include any header fields that indicate optional features implemented by the server and applicable to that resource  e g   Allow   possibly including extensions not defined by this specification  The response body  if any  SHOULD also include information about the communication options  The format for such a body is not defined by this specification  but might be defined by future extensions to HTTP  Content negotiation MAY be used to select the appropriate response format  If no response body is included  the response MUST include a Content-Length field with a field-value of  quot 0 quot   The Max-Forwards request-header field MAY be used to target a specific proxy in the request chain  When a proxy receives an OPTIONS request on an absoluteURI for which request forwarding is permitted  the proxy MUST check for a Max-Forwards field  If the Max-Forwards field-value is zero   quot 0 quot    the proxy MUST NOT forward the message  instead  the proxy SHOULD respond with its own communication options  If the Max-Forwards field-value is an integer greater than zero  the proxy MUST decrement the field-value when it forwards the request  If no Max-Forwards field is present in the request  then the forwarded request MUST NOT include a Max-Forwards field  9 4 HEAD The HEAD method is identical to GET except that the server MUST NOT return a message-body in the response  The metainformation contained in the HTTP headers in response to a HEAD request SHOULD be identical to the information sent in response to a GET request  This method can be used for obtaining metainformation about the entity implied by the request without transferring the entity-body itself  This method is often used for testing hypertext links for validity  accessibility  and recent modification  The response to a HEAD request MAY be cacheable in the sense that the information contained in the response MAY be used to update a previously cached entity from that resource  If the new field values indicate that the cached entity differs from the current entity  as would be indicated by a change in Content-Length  Content-MD5  ETag or Last-Modified   then the cache MUST treat the cache entry as stale

[php] RESTful API methods; HEAD & OPTIONS

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