php - Get a certain part of a changing string -

i have this:

"https://example.com:443/commonauth/?sessiondatakey=2aeeaf42-83d8-4b90-b8b4-39c1856c7de2&type=oauth2" 

now want string sessiondatakey.
how extract part string if length of string different every time?

if want sessiondatakey string can way

<?php     $string = "https://example.com:443/commonauth/?sessiondatakey=2aeeaf42-83d8-4b90-b8b4-39c1856c7de2";      preg_match("/sessiondatakey=([a-z0-9\-]*)(&|$)/", $string, $result);      echo $result[1]; 

([a-z0-9-]+) - match 1 or more characters a-z, numbers 0-9 , dash

(&|$) - after previous match comes character & or end of string

if want sessiondatakey url can way

<?php     $sessiondatakey = $_get['sessiondatakey'];      echo $sessiondatakey; 

this classic way of getting parameters url. more here.