To communicate some data to functions inside adminer $_SESSION is used. In adminer/include/bootstrap.inc.php line 39 the call to session_cache_limiter() will cause a warning in PHP 7.2. This function can only be used before starting a session.
This warning is also output in ajax calls which now produce invalid JSON data.
The warning cannot be suppressed because the script itself sets error_reporting(6135); in the first line.
In line 40 there is a check to see if the constant SID is not defined yet. Should the call to session_cache_limiter() be moved inside that block? Alternatively the error_reporting level could be changed to suppress warnings.
Fixed in Git, thanks.