Do Not Micro-Optimize
Whenever I read blog postings such as that one (in the spirit of John McCain's that one reference to Barack Obama) I get a little bit angry.
"calling a static method is faster than an object method"
It is called Object-Oriented Programming. Not "Class-Oriented Programming". Nor "Procedural Progamming with Classes as Namespaces".
The small performance gain you may or may not get at deployment-time by using static method calls instead of using instance method calls comes at the price of problems at development-time.
One of the problems at development-time that you are digging yourself into is that of untestable code: static methods are death to testability. Use them when it makes sense to use them and not because you think you can improve the performance of your website by using them.
I bet that your problems lie elsewhere when you think that you can solve them by a micro-optimization such as this. Have a look at Ilia's Common Optimization Mistakes slides for more information on this topic.