Karl, Will and I all use them throughout our projects. Will posted a thread on the actual prefixes over in
this thread many months ago, which you may find interesting. Our prefixes are not strictly correct because we use
sz for strings. In our opinion,
$szString looks prettier than
$sString, and so we're victims of aesthetics in that instance. Naughty us!
However, considering I use them, I may be somewhat biased, so please excuse me. Nonetheless, the reason I use variable prefixes is so I can immediately identify what a variable should contain. It doesn't just have its readability advantages, but rather you can automatically filter data based on the prefixes. So if I have a variable called
$iNumber then I could enforce that data type to be an integer. It often works well in passing the items from POST and GET.
The variable prefixes are actually nothing new. They're officially called Hungarian notation, and
Wikipedia has an impartial page all about them. At the end of the day, it all comes down to personal preference. We can argue for and against for years to come.