I have a Mandrake 9.1 installation that I am attepmting to install PHP4 
on. I start with the following tarball, php-4.3.4.tar.gz.Unzipping and 
un taring go fine, but when I go to ./configure , I get an error message 
as follows, 

checking for flex... lex
checking for yywrap in -ll... no
checking lex output file root... ./configure: line 2425: lex: command 
not found
configure: error: cannot find output from lex; giving up

I then opened up the configuration file and went to line 2425 and find 
the following:

  # The minimal lex program is just a single line: %%.  But some broken 
lexes
# (Solaris, I think it was) want two %% lines, so accommodate them.
echo '%%
%%' | $LEX
if test -f lex.yy.c; then
  ac_cv_prog_lex_root=lex.yy
elif test -f lexyy.c; then
  ac_cv_prog_lex_root=lexyy
else
  { echo "configure: error: cannot find output from $LEX; giving up" 
1>&2; exit 1; }

My interpretation of this is that my installation doesn't have lex 
installed. Does this make sense? If this is so, what is lex and how can 
I get it?  Is there any other reason why this install may be failing?

Normally, if I wanted PHP to be installed, I would just either install 
it at the time I was installing the operating system, but this time i 
deliberatly did not install it as I am working through "Sams teach 
yourself  PHP MySQL and Apachee in 24 hours" and the installation is 
part of the learning process. As with all education, you never know what 
you may have to learn in order to learn what you are trying to learn.

Charlie