Troubles with phpize

First of all... hi everybody, i'm new in this list :) Ok, i'm interested in developing extensions for php, so i got the sources of php 5, and begin reading some tutorials... the problem came when i run phpize, in order to get a configure script... I get an error and some warnings, here is: ayoze@tequila:~/Descargas/php-5.0.1/ext/php5cpp$ phpize Configuring for: PHP Api Version: 20031224 Zend Module Api No: 20040412 Zend Extension Api No: 220040412 acinclude.m4:19: warning: underquoted definition of PHP_PROG_RE2C run info '(automake)Extending aclocal' or see http://sources.redhat.com/automake/automake.html#Extending%20aclocal acinclude.m4:1903: warning: underquoted definition of PHP_TEST_BUILD /usr/local/share/aclocal/imlib.m4:9: warning: underquoted definition of AM_PATH_IMLIB /usr/local/share/aclocal/imlib.m4:167: warning: underquoted definition of AM_PATH_GDK_IMLIB /usr/local/share/aclocal/glib-gettext.m4:378: warning: underquoted definition of AM_GLIB_GNU_GETTEXT /usr/local/share/aclocal/glib-gettext.m4:379: warning: underquoted definition of AM_GLIB_DEFINE_LOCALEDIR /usr/local/share/aclocal/glib-2.0.m4:8: warning: underquoted definition of AM_PATH_GLIB_2_0 configure.in:65: error: possibly undefined macro: AC_PROG_LIBTOOL If this token and others are legitimate, please use m4_pattern_allow. See the Autoconf documentation. I try to find something about it in google, but nobody seems to have reached the solution to solve it. The first time i thought the problem was in the config.m4 i did... but I tried to phpize another extension (sockets or mysql) and I got the same error. Does somebody know what's my problem? Cheers, Ayoze