In a new pointer from PHP Magazine:

When developers start talking about minding their P's and Q's, they might just be referring to scripting languages that are proving their worth next to more established counterparts. PHP, Perl, and Python (the P-Languages) have really come into their own over the last four or five years because of their ability to augment general-purpose programming languages, such as C++, Java, and C# (sometimes called the G-Languages), according to IT research firm Burton Group. The firm's report suggests P-Languages are performing well enough in mission-critical tasks like enterprise scripting that they should be preferred over their G-Language counterparts.

In the report, analyst Richard Monson-Haefel points out that PHP makes dynamically generating HTML and processing HTTP requests very easy. Perl is frequently used for batch transformations of text data and in the system administration of Unix and Linux systems. Python is frequently used as "glue" code as well as for system administration, text processing, and even application development. Read more...

He does make an important note, however - while the languages Perl and Python are about as susceptible to hacker attacks than most other languages, PHP, while just as secure itself, has a bad trend of software that's notorious for being insecure (you know who you are). There's even mentionm of the PHP Security Consortium that's called a "good first step in the right direction for the PHP community."