Lors de l?installation de ffmpeg-php et que vous tapez phpize et que ça vous donne cette erreur :

$ phpize
configure.in:9: warning: underquoted definition of PHP_WITH_PHP_CONFIG
run info ?(automake)Extending aclocal?
or see http://sources.redhat.com/automake/automake.html#Extending-aclocal
configure.in:32: warning: underquoted definition of PHP_EXT_BUILDDIR
configure.in:33: warning: underquoted definition of PHP_EXT_DIR
configure.in:34: warning: underquoted definition of PHP_EXT_SRCDIR
configure.in:35: warning: underquoted definition of PHP_ALWAYS_SHARED
acinclude.m4:19: warning: underquoted definition of PHP_PROG_RE2C
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.

Le problème est dû que libtool n?est pas installé

$ yum list|grep -i libtool
libtool-libs.i386 1.5.6-4.EL4.1.c4.4 installed
libtool.i386 1.5.6-4.EL4.1.c4.4 base
$ yum install libtool

Et le tour est joué