`static` vs `self`

staticVsSelf.php

<?php

class VarHolder {
  const VAR = 2;

  public function showVar() {
      echo self::VAR;
      echo static::VAR;
   }
}

staticVsSelfInheritance.php

<?php

class ChildVarHolder extends VarHolder {
  const VAR = 4;

  public function doSomething() {
      echo self::VAR;
      echo static::VAR;
   }
}