It would be very nice if we could have "bulk replacement feature" something like the following command in the future. 
find . -name "*.php" -exec sed -i 's/before/after/g' {} \;
In reply to Mitsuhiro Yoshida
Re: bulk replacement
{$a->নাম} - {$a->তারিখ} দ্বারা
Yes, that is definitely planned. Strings after such operation would go to the stage to be reviewed before the commit.