Summary:
when using include, __FILE__ prepends / to relative paths

History:
Received errors from imp3.0 saying could not find included file. Error message reported strange path names. See Horde bugs #911 and #912.

Sample Code:
a.php =>

<?php 
  echo "Calling  file ", __FILE__; 
  echo "<br>included as lib/a.php reports "; 
  include 'lib/a.php'; 
  echo "<br>included as ./lib/a.php reports "; 
  include './lib/a.php'; 
  echo "<br>included as /www/yacc/tmp/lib/a.php reports "; 
  include '/www/yacc/tmp/lib/a.php'; 
?> 

lib/a.php => 

<?php 
    echo  __FILE__; 
?> 

When I do this, I get 

Calling file /www/yacc/tmp/a.php 
included as lib/a.php reports /lib/a.php 
included as ./lib/a.php reports /lib/a.php 
included as /www/yacc/tmp/lib/a.php reports /www/yacc/tmp/lib/a.php 

Something keeps putting a leading / on relative paths!

Other Tests:

I created a simple C program to print out the __FILE__ value. When is compile it with HP's ANSI C compiler it works as expected i.e. the value is as specified in the include. When I compile with GNU CC compiler (gcc) the value is "sanitised". 
 
See below 

/home/gedl/tmp $ cc -o a a.c ./lib/b.c && echo "The output" && ./a 
a.c: 
./lib/b.c: 
The output 
a.c 
./lib/b.c 
/home/gedl/tmp $ gcc -o a a.c ./lib/b.c && echo "The output" && ./a 
The output 
a.c 
lib/b.c 
/home/gedl/tmp $ 
 
Essentially the same but not exactly. However both compilers give a valid answer.

I will continue to work on it but if someone has an answer it would be appreciated.

Cheers

Ged