Hello, The configure system for php-solr seems to have a (short) hard-coded list of prefixes where to look for an include directory. These do not consider multi-arch locations, thus curl headers are not found.
A better way would be to use pkg-config and query the needed cflags and libs from libcurl.pc, this isn't done either.... Implementing either of the above should solve this issue. Regards, Andreas Henriksson