php - mbstring function overload using ini_set() -

i want able set mbstring.func_overload within php file using ini_set(), example:

ini_set( 'mbstring.func_overload', 7 ); $foo = 'é'; echo "expected output: 1 1\n" , "output: " , strlen( $foo ) , mb_strlen( $foo ); 

outputs:

expected output: 1 1 output: 2 1 

on manual page says:

this setting can changed php.ini file.

this explains unexpected behaviour. should instead?