I have a web site (not by wordpress ) how can I create a squeeze page? https://www.eleectroforce.net

https://www.ads-software.com/plugins/squeeze-page-toolkit/

Fatal error: Call to undefined function json_last_error() in /home/content/56/5553956/html/wp-content/plugins/squeeze-page-toolkit/lib/common.inc.php on line 206

any ideas on how to resolve this?

https://www.ads-software.com/plugins/squeeze-page-toolkit/