As pecl/http 1.0 has finally been released and I had noticed that it's been packaged already by several projects like PLD, Gentoo and FreeBSD, I wanted to explain what one is going to gain respectively lose by using the different build/configure options for the extension.
The help text of configure for pecl/http should look similar to the following:
--enable-http Enable extended HTTP support
HTTP: with cURL request support
HTTP: with zlib encodings support
HTTP: with magic mime response content type guessing
--with-http-shared-deps HTTP: disable to not depend on extensions like hash,
iconv and session (when built shared)
If you link the extension source directory into your php tree, you should be aware that these options show up on the end of the list of configure options for extensions, not--as probably expected--in alphabetical order. This is due to a recent change to use config9.m4 because the HTTP extension may depend on several other PHP extensions (hash, iconv, session).
This configure option enables request functionality, uses libcurl and is highly recommended to be enabled. The minumum libcurl version required is 7.12.3. Debian/stable currently ships 7.13.2 (no, this is not a typo).
I think this is the most overseen/ignored option. Besides handling of compressed HTTP messages, it also provides superior deflate/inflate functionaly in regards to stability and performance compared to the standard zlib extension. Both http_deflate()/http_inflate() functions and http.deflate/http.inflate stream filters are able to encode/decode all valid gzip, zlib (AKA deflate) and raw deflated data. It requires at lieast libz version 126.96.36.199, while Debian/stable ships 1.2.2, and is also highly recommended to be enabled.
This option enables content type guessing for the HttpResponse and HttpMessage classes. It's rather a gimmick and thus not enabled by default. As there's no version information available for libmagic, I don't even know which is the minimum version required but I guess anything coming from a file-4.1x versioned package should work. If you get an empty string as content type for payload which is obviously XML text, check the magic.mime database you use for a broken first XML section. Comment out everything except the SVG detection as other XML types and HTML is handled further down the magic file (noticed on Debian systems). If you changed your magic.mime database, don't forget to regenerate the precompiled version with the `file -C`command.
This option controls whether pecl/http will depend on extensions built as dynamically loadable modules. So, if e.g. ext/iconv has been compiled shared, pecl/http relies on ext/iconv to be loaded when itself is going to be loaded. This option is enabled by default.
pecl/http uses ext/hash to generate ETag hashes (else standard PHP MD5, SHA1 or CRC32).
http_redirect() can automatically append session information to the redirect URL.