This script get PHP gettext string (finds the "__" function) and merges them in .po files.

__mergetool.sh

#!/bin/bash

XGETTEXT=/usr/bin/xgettext
XMESGMERG=/usr/bin/msgmerge
DOMAIN="messages.po"
TEMPLATE="messages.pot"


if [ ! -e "$1" ]; then
    touch $1
fi

find . -type f -iname "*.php" -o -iname "*.phtml" | $XGETTEXT -p $1 -o $TEMPLATE -L php -j --keyword=__ -n --from-code=utf-8 -f - 

find $1 -type f -iname $DOMAIN > ./messages.tmp

while read fichier
do 
	$XMESGMERG -o $fichier $fichier "$1/$TEMPLATE"
done < ./messages.tmp