Absolutely not bashscript! No -- for many, many reasons -- NO!. Now that we have that out of the way, I'll discuss reasonable languages for the project.
Now, I wouldn't even recommend PHP for this. I'll try to go over it point by point:
1. Most languages will work fine for this.
2. Again, many languages will work. At this point, it's looking like Java, Python, or maybe C++ would be OK.
3. Security has almost nothing to do with the language.
4. For speed, C and C++ are the tops. These days, though, Java is really quite fast. Python, Ruby, and Perl are slower.
5. Since when do you need PHP for this? Java, Ruby, Python, Perl, also all work.
6. Easy-to-understand cancels out C++ and Perl, in my opinion. Java is fairly easy to understand, and so is Python. Both of these languages have extensive libraries and third-party packages, so there's no rebuilding the wheel.
I hope that helps. I would be glad to answer any further questions.