PHP static method slower than objet method

This is the PHP code...

class SomeClass
{
   static function doTest($var) {return $var;}
}

class SomeObj
{
   function doTest($var) {return $var;}

   static function doTest2($var) {return $var;}
}

//bench static call
$starttime = microtime(true);
for ($i = 0; $i< 100000; $i++)
   SomeClass::doTest($i);
echo "Static call time: " , (microtime(true)-$starttime) , " ms
"; //bench object method $starttime = microtime(true); $obj = new SomeObj(); for ($i = 0; $i< 100000; $i++) $obj->doTest($i); echo "Object method call time: " , (microtime(true)-$starttime) , " ms
"; //bench static call $starttime = microtime(true); for ($i = 0; $i< 100000; $i++) SomeObj::doTest2($i); echo "Static call (when the static is in the same class of object method) time: " , (microtime(true)-$starttime) , " ms
";

...and these are the results (simply reload page to do another test):

Static method call time: 0.041136026382446 ms
Object method call time: 0.030946016311646 ms
Static method call (when the stati method is in the same class of object method) time: 0.038840055465698 ms