Question

What are some of the most expensive operations in PHP? I know things like overusing the @ operator can be expensive. What else would you consider?

Answer 1

• serialize() is slow, as is eval(), create_function(), and spawning additional processes via system() and related functions.
• beware of anything APC can’t cache — conditional includes, eval()ed code, etc.
• Opening database connections. Always cache your connections and re-use them.
• Object cloning
• Regular expressions. Always use the normal string operations over a regular expression operation if you don’t need the functionality of a regexp, e.g. use str_replace() over preg_replace() where possible.
• Logging and disk writes can be slow – eliminate unnecessary logging and file operations

Some micro-optimizations that are good practice, but won’t make much difference to your bottom line performance:

• Using echo is faster than print
• Concatenating variables is faster than using them inline in a double-quoted string.
• Using echo with a list of arguments is faster than concatenating the arguments. Example: echo 'How are you ',$name,' I am fine ',$var1 is faster than echo 'How are you '.$name.' I am fine '.$var1
• Develop with Notices and Warnings turned on. Making sure they don’t get triggered saves PHP from having to run error control on them.