We’re running iThemes Security with PHP 7.4.2. No issues.
Have you tried deleting the plugin, clearing cache (local and global), then reinstalling it?
Before reinstalling the plugin, make sure the plugin database tables (cPanel) have been deleted as well.
Cheers!
error_reporting
PHP 5.3 or later, the default value is:
E_ALL & ~E_NOTICE & ~E_STRICT & ~E_DEPRECATED
This setting does not show E_NOTICE, E_STRICT and E_DEPRECATED level errors. You may want to show them during development.
Prior to PHP 5.3.0, the default value is:
E_ALL & ~E_NOTICE & ~E_STRICT.
This bug (2 occurrences) has been fixed in the 6.4.0 iTSec Pro release.
According to the iTSec Pro 6.4.0 Changelog:
Bug Fix: Warning when loading the settings page on PHP 7.4.
Bug Fix: Warning when loading the debug page on PHP 7.4.
So this (only the first occurrence) is still an issue in the free iTSec plugin.
To prevent any confusion, I’m not iThemes.
Actually these are both still an issue in the free iTSec plugin (7.6.1).
Apparently iThemes missed the second occurrence of the implode() function deprecation in the Pro plugin (ithemes-security-pro/pro/dashboard/class-itsec-dashboard-util.php #789).
Note these deprecation notices will only show if the WP_DEBUG constant is set to true in the wp-config.php file.
To prevent any confusion, I’m not iThemes.