REGEXP different from 2 similar servers

I have a php installed as: './configure' '--prefix=/usr' '--with-apxs=/usr/sbin/apxs' '--with-gd' '--with-gettext=/usr' '--enable-safe-mode' '--with-config-file-path=/etc/httpd' '--with-exec-dir=/usr/bin' '--with-zlib' '--enable-magic-quotes' '--with-regex=system' '--with-ttf=/usr/lib/libttf.so' '--enable-track-vars' '--enable-xml' '--disable-debug' '--with-db3' '--with-interbase=shared' '--with-pgsql=shared' '--with-ldap' '--with-imap' and a second one installed as: './configure' '--with-apxs=/var/lib/apache/sbin/apxs' '--enable-trans-sid' '--with-regex=system' and it seems that ereg and ereg_replace work in a different way. In the second one works ok, in the first none of my ereg are recognized. Can anyone help ? Could it be the "magic-quotes" ?