Try something as follows (set db name, username and password)
Code:
#!/bin/bash
DBNAME="phpbb"
DBPASS="myPassWord"
DBUSER="admin"
DBHOST="localhost"
BACKUP="out.sql"
>$BACKUP
echo ""
echo -n "*** Dumping tables to $BACKUP file : "
TABLES=$(mysql -ss -h $DBHOST -u $DBUSER -p$DBPASS $DBNANE -e'show tables like "phpbb_%";')
for t in $TABLES
do
echo -n " $t "
mysqldump -h $DBHOST -u $DBUSER -p $DBPASS $DBNAME --tables "$t" >> $BACKUP
done
echo " *** Done."