For a look at both sides of the argument in one place, see: PhpProsAndCons
PHP is a notably simple language: the effort of learning PhpLanguage is trivial if you already know CeeLanguage or CeePlusPlus. It now provides a class system very like C++'s. Database and web integration are unusually strong. Cross-platform support and the availability of languages are excellent. PHP has good RegularExpressions and AnonymousFunctions.
Compared to PerlLanguage, PHP is much simpler.
Compared to PythonLanguage, PHP is much more C-like. But since when was being "much more C-like" an advantage, and if it is, then why aren't you simply using C? Python's advantage over PHP is that it's "much more LispLanguage-like", having closures, sensible scoping rules, etc. Being "much more C-like" sounds like a big step backwards.
Compared to all of the above, PHP arguably has much simpler webpage integration, and programmers are easier to find (with the possible exception of Perl). However, the other 3 big scripting languages may still have advantages that make them more suitable for "heavy lifting" non-website jobs.
PHP provides a handy way of packing a bunch of variables for passing them around as single unit (an associative array), with little performance penalty. It leaves more freedom than using pre-defined structures with explicitly enumerated fields. Check out PHP manual for compact() and extract() functions. --DexenDeVries
and parse_str() and http_build_query()