php - how to make $_SESSION['something'] and adding a $ before it to make it a var. it doesn't work -

hi need thing. defined session var , when tried echo $_session['lang'] var didn't work @ all. , of corse had page.php?lang=eng'

    $eng = "this english. yey";     if(empty($_get['lang'])){     $_session['lang'] = $eng; }else{     $_session['lang'] = "$" + $_get['lang']; } 

i guess supposed give me var $eng, had defined , still nothing happened. please help.

i can't see reason want php: variable variables:

$_session['lang'] = ${$_get['lang']};