hi Zenghui,
I suppose everybody has their preferences with scripting languages.
I prefer to use PHP mainly I because the language pretty well. For smaller jobs I use Perl. The strength of PHP/Perl is that it is very well integrated with web, which at the same time is a weakness.
If you need to program something that needs a graphical interface (like a form with textfields, etc), then making some web pages with PHP/Perl and mySql for data storage is great.
For example, for one paper I was categorizing the narrative of NT filings (late filings). The script retrieved the relevant part, output it to a web page. I had a form with checkboxes etc, that I filled in and after submitting it showed the next filing. (This works faster than entering the info in Excel).
If you need no human interaction (the script can run by itself), then Python would probably be better.
I have one colleage that uses Python for web data harvesting (which could have been done in PHP/Perl as well). I suppose Python is (much) easier to use than Perl. I think the ‘object oriented’ part of Perl is not intuitive.
Historically, content analysis (pattern matching) comes from Perl, but other languages usually support this. Even SAS has some pattern matching. 
I have never heard of Ruby, actually.
best regards,
Joost