Amazon Linux pecl_http installed but not providing functions
Solution 1:
Maybe a little late, but perhaps this helps someone else landing here...
Insure that you are referencing the correct version of the pecl_http API. They moved to namespaces in v2, so the calling convention is quite different. Much of the documentation around on the web references methods in v1.
http://devel-m6w6.rhcloud.com/mdref/http
Solution 2:
Please try
strace -fF -o /tmp/wtf php your_php_script.php
And then comb through /tmp/wtf
file with a text editor/viewer/grep variant of your choice to see 1) proper php.ini was read and 2) if http.so extension was actually loaded.