PHP is an extremely popular and almost ubiquitous server side scripting language. Many PHP developers discover that it can also be used as a command-line scripting language.
The advantage of using PHP for both server side scripting and command-line scripting (for say cronjobs) is that you can share library code between the 2 environment and only have to write your libraries once.
My PHP Experience
I started coding in PHP back in the days of PHP 3 cira 1998.
I have found that the biggest source of bugs in my PHP code is due to the lack variable declaration. Most bugs I have (unintentionally) put in my code always seem to be due to misspellings. Namespaces in PHP would also be nice.
For those who require pushing the limits of their systems and are looking to speed up PHP execution, I can vow for PHP Accelerator. I have used it and found that it works and is stable on the systems I have it on. (Although I have found that the speed increase is minimal in comparison to optimization from database bottlenecks and computation complexity.)