As others have reported, setting --enable-discard-path does not allow PHP to run properly in CGI mode.  This simple script will fail when hit through a Web server:

#!/usr/local/bin/php

<?php echo "Hello, world."; ?>

producing a "No input file specified" error.

There seem to be three bugs in the file sapi/cgi/cgi_main.c that cause this.  (At least, when I fixed these things, it worked).  I'll now reveal what is probably my ignorance of the code by pointing them out.

The problems are all in the init_request_info() function.  Specifically,

1.  ~Line 252.  script_filename is set to getenv("SCRIPT_FILENAME") rather than getenv("SCRIPT_NAME").  Maybe SCRIPT_FILENAME is a newer variant I haven't heard of, but our servers have always used SCRIPT_NAME.

2.  ~Line 278.  If DISCARD_PATH is set and script_filename is available, SG(request_info).path_translated should be set to the concatenation of getenv("DOCUMENT_ROOT") and script_filename, not just script_filename.  Otherwise, when php_fopen_primary_script() tries to open it it will bomb, because it doesn't have the full path.

3.  ~Line 290.  For some reason, irrespective of the previous DISCARD_PATH section, SG(request_info).path_translated is set to NULL.  This will clobber the script name when discard path is enabled.  As far as I can tell this line should simply be removed.


Hope that's useful to someone. :)