PHP 7.4 (or even better, 8.1 support)

[krisgermann]

There are a number of deprecated functions in the init.php and some other scripts that are causing errors, example:

2023/03/02 17:11:27 [error] 185747#185747: *5 FastCGI sent in stderr: "PHP message: PHP Fatal error: Uncaught Error: Call to undefined function simplexml_load_string() in /usr/local/playsms/html/lib/fn_core.php:860
Stack trace:
#0 /usr/local/playsms/html/plugin/core/gateway/fn.php(197): core_xml_to_array('<?xml version="...')
#1 /usr/local/playsms/html/plugin/core/gateway/gateway.php(210): _gateway_display()
#2 /usr/local/playsms/html/inc/app/main.php(33): include_once('/usr/local/play...')
#3 /usr/local/playsms/html/index.php(34): include('/usr/local/play...')
#4 {main}
thrown in /usr/local/playsms/html/lib/fn_core.php on line 860" while reading response header from upstream, client: xxx.xxx.xxx, server: _, request: "GET /index.php?app=main&inc=core_gateway&op=gateway_list HTTP/1.1", upstream: "fastcgi://unix:/run/php/php7.3-fpm.sock:", host: "sms.portalnetworks.ca", referrer: "http://xxx.xxxxx.xxx/index.php?app=main&inc=core_user&route=user_mgmnt&op=user_list"