<?php
$jsndata = '{
"success":true,
"data":"{\"campaign_name\":\"helloworld\",\"download_link\":\"https:\\\/\\\/google.com\\\/accesskey\\\/getfile\\\/m-spqn-e61-2aef2575a0b5250354f2b0fda033e703?token=HUSYjdC5jyJskXUHiKn13l1A1BaAjH2R&dcma=5ecceb0522bcd0db\",\"link\":\"http:\\\/\\\/www.lol.com\\\/remove\\\/remove.php\"}",
"message":null
}';
// Decode the main json object
$jsn = json_decode($jsndata,true);
// Since 'data' is another serialized object, you need to decode that as well:
$data = json_decode($jsn['data'], true);
// Now you can access the contents of 'data'
echo $data['download_link'];
Warning: PHP Startup: Unable to load dynamic library 'sodium.so' (tried: /usr/lib/php/8.3.5/modules/sodium.so (libsodium.so.23: cannot open shared object file: No such file or directory), /usr/lib/php/8.3.5/modules/sodium.so.so (/usr/lib/php/8.3.5/modules/sodium.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0
https://google.com/accesskey/getfile/m-spqn-e61-2aef2575a0b5250354f2b0fda033e703?token=HUSYjdC5jyJskXUHiKn13l1A1BaAjH2R&dcma=5ecceb0522bcd0db