title: When to use and not to use static function?
body: <p>My colleage says static is good when you perform fixed stuff that doesn't required any extends, but one day we need to add feature on top of his code. Heck we have to modify the ori code because he used tons of static stuff and it's not flexible for us to continue.</p>
  
  <pre><code>class test {
      public static function test1() {
          echo 'hi';
      }
  }
  test::test1();
  </code></pre>
  
  <p>Why should one should use static function? When to use it and not to use static function?</p>