我不知道如何解决这样的编译问题

keer2345

checking whether ln -s works... yes
checking if compiler supports -R... no
checking if compiler supports -Wl,-rpath,... yes
checking for re2c... re2c
checking for re2c version... invalid
configure: warning: You will need re2c 0.9.11 or later if you want to regenerate PHP parsers.
checking for gawk... gawk
checking for bison... bison -y
checking for bison version... 1.875 (ok)
checking for flex... lex
checking for yywrap in -ll... no
checking lex output file root... ./configure: line 3246: lex: command not found
configure: error: cannot find output from lex; giving up

debian:/opt/php-5.1.6# make
make: *** 没有指明目标并且找不到 makefile。 停止。
debian:/opt/php-5.1.6#




求助！！！！！！！！！！！！！！

manphiz

安装flex