如何从laravel刀片获取变量值文件

I have a hidden field in laravel blade.

 <input type="hidden" name="agencyid" value="{{Auth::user()->agency_id}}" />

How will i get the value of this variable "agencyid" and assign to another variable? Like

$agency=$agencyid;

Iam trying to pass this value to an external PHP file.

   <?php include($_SERVER['DOCUMENT_ROOT'].'/core/agency_expiry.php?agency=$agency'); ?>

Iam new to laravel so exploring the same.