PHP is probably the language with the best return on investment (of time spent learning) currently. It is extremely easy, and is fast to prototype stuff because of the high level nature. While the language is not as expressive as other languages such as Ruby or Python, it is easy to move on later, but PHP provides everything to get things done and deploy easily your simple application in minimal time.
A lot of good programmers today started their web experiences with PHP. Now probably they are using the latest cool thing, but it served as the "BASIC" of our times, and is still active and trying to fix its issues.
Also, and this is not a PHP merit, but a disaster with other dynamic languages such as Ruby, the performance you get by default with a simple PHP application, is good enough that is almost always the DB to blame, not the front-end, when there are issues under load.
A lot of good programmers today started their web experiences with PHP. Now probably they are using the latest cool thing, but it served as the "BASIC" of our times, and is still active and trying to fix its issues.
Also, and this is not a PHP merit, but a disaster with other dynamic languages such as Ruby, the performance you get by default with a simple PHP application, is good enough that is almost always the DB to blame, not the front-end, when there are issues under load.