variable variable syntax change?

Hi; Q: Did the variable variable syntax change in php v 5.6x? I am aware it has changed in v 7.0 (or is there probably something else wrong with my code? Something has gone haywire and I am not getting any errors accept for the browser complaining the css is sent as text/plain instead of text/css. That is because the reference to the css source is not happening. That is because the variable variable references are failing, apparently) I have code that has been working fine until I got a copy of the site and installed it on a local FreeBSD server with php v 5.6.0 There are references to an array containing array names as strings that are supposed to fetch the values in the arrays indicated by array name as a string. Further, these are associative arrays that can be used as a database to access values by string index. $_subLst = ${self::$_arrayNames[$_dep]}; print "sub: ".$_subLst."\n"; //// $_subLst is empty require_once( ${$_depts}[$_dep] ); // $_depts points to $_departmentDefaults['departments'] // witch is '_deptDefaults' that points to source files containing all the necessary department related html // and css and javascript source. example: $_arrayNames['invention'] = '_inventionSub'; // points to $_inventionSub; // where there is, for example, an entry: $_inventionSub['Furniture'] = './?d=invention&sub=furniture'; These strings would be used to construct get query strings appended to anchor tag href values. Thanks for time and attention: Jeff K