安装php时出错，麻烦各位看一下。

[root@server php-4.3.1]# ./configure --prefix=/server/php --with-apxs=/server/apache/bin/apxs --with-config-file-path=/usr/l
ocal/lib --enable-track-vars --with-xml --with-mysql=/server/mysql
loading cache ./config.cache
checking for Cygwin environment... no
checking for mingw32 environment... no
checking for working sed... sed
checking host system type... i686-pc-linux-gnu
checking for gcc... gcc
checking whether the C compiler (gcc  ) works... yes
checking whether the C compiler (gcc  ) is a cross-compiler... no
checking whether we are using GNU C... yes
checking whether gcc accepts -g... yes
checking whether gcc and cc understand -c and -o together... yes
checking how to run the C preprocessor... gcc -E
checking for AIX... no
checking if compiler supports -R... no
checking if compiler supports -Wl,-rpath,... yes
checking for ranlib... ranlib
checking whether ln -s works... yes
checking for gawk... gawk
checking for bison... no
checking for byacc... no
configure: warning: You will need bison if you want to regenerate the PHP parsers.
checking for flex... lex
checking for yywrap in -ll... no
checking lex output file root... ./configure: lex: command not found
configure: error: cannot find output from lex; giving up


最后一句话什么意思啊？　　　　　　

自己顶一下，麻烦了