system(): access denied

Hello All, I have a script which uploads a mysqldump file into the server and use system("mysql -uroot -p < the_dump_file.sql") to restore the database. While, it does not go through and the apache error_log shows: Enter password: Enter password: ERROR 1045: Access denied for user: 'root@localhost' (Using password: YES) The passwords for mysql account "root" is "", but when I remove the -p from the command, everything is fine. The wired thing is, when I use system("mysqldump -uroot -p >the_dump_file.sql"), it is also fine. Anybody has experience of this? or any suggestions? Thanks a lot.