How do I call a subfunction from another subfunction of an object in PHP? -

how call subfunction subfunction of object in php, this:

class object {      function function1(){           return dosomething(data);      }       function function3(){           function function2(){                function1(data);           }      } } 

?

i trying , error fatal error: call undefined function convertmonthstringtonumber(), convertmonthstringtonumber() being function1() in example code.

you can call through $this psuedo-variable.

$this->function1();