I decided to recall some features of PHP related to performance.
I will note that I included in my small list only what is usually surprising to junior developers with whom I had to work. I think everyone knows about banal things like “single quotes instead of double quotes”, so I will try to surprise anyone. ')
The results and conclusions are made on the basis of several versions of PHP, which revolve on servers I know, namely 5.2.6 from Debian Lenny, 5.3.2 from Ubuntu, and 5.2.14 from dotdeb. Perhaps on other platforms, there are differences.