PHP micro-optimization tips

• calling an object method is faster then traping it with with "__call"
• calling a "static" method is faster then an object method
• calling a function is faster then calling a static method
• accessing a local variable is faster then then a global variable
• accessing a global variable is faster then an object property
• accessing an object property is faster then trapping it with "__get" and "__set"
• accessing an initialized variable is faster then accessing an uninitialized variable
• absolute paths in "include" and "require" are faster then relative
• merging several scripts in one file and then including it is faster then several includes
• "switch" is faster then "if ... else if ..." in some cases
• do not use regexs for simple string processing tasks
• avoid @ (error control operator)
• avoid notices and warnings in your scripts
• avoid unused variables and unused method parameters
• adding method parameter increases calling time
• adding method parameter type hint increases calling time
• unset variables that contain large amount of data or circular references
• $_SERVER['REQUEST_TIME'] contains script startup time
• cache page output or result of resource-consuming functions
• "echo" is faster than "print"
• "echo" accepts several arguments, you can use it instead of string concatenation
• "ob_start()" and "ob_end_clean()" is may be better then several string concatenations
• strings in single quotes ('...') are processed faster then strings in double quotes ("...")
• pre-increment (++$i) is faster then post-increment ($i++)
• "isset" is a faster alternative to "array_key_exists"
• an array is a faster alternative to a class with several fields
• "foreach" is better then "for" in many cases
• open resources (files, database connections, sockets) right before using them, free resources as soon as you do not need them
• do not fetch database fields which you do not use in your script
• use prepared database statements
• combine several queries in one when database supports it