postrm is in php-horde 5.1.5+debian1-1.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20  | #!/bin/sh
set -e
dpkg-maintscript-helper mv_conffile \
    /etc/apache2/conf.d/horde.conf /etc/apache2/conf-available/php-horde.conf 5.1.0+debian0-1~ -- "$@"
if [ "$1" = "remove" ] || [ "$1" = "purge" ] ; then
        CONF="php-horde"
        COMMON_STATE=$(dpkg-query -f '${Status}' -W 'apache2.2-common' 2>/dev/null | awk '{print $3}' || true)
        if [ -e /usr/share/apache2/apache2-maintscript-helper ] ; then
                . /usr/share/apache2/apache2-maintscript-helper
                apache2_invoke disconf $CONF || exit $?
        elif [ "$COMMON_STATE" = "installed" ] || [ "$COMMON_STATE" = "unpacked" ] ; then
                [ ! -L /etc/apache2/conf.d/$CONF.conf ] ||  rm /etc/apache2/conf.d/$CONF.conf
        fi
fi
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