PHP 8.1 で Moodle 4.0 を入れようとしたときのエラー：
PHP 8.1 （Ubuntu 22.04でのPHPの標準バージョン）で Moodle 4.0 を入れようとしたときのエラー：
PHP Deprecated: Return type of moodle_recordset::rewind() should either be compatible with Iterator::rewind(): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/html/moodle/lib/dml/moodle_recordset.php on line 61
Deprecated: Return type of moodle_recordset::rewind() should either be compatible with Iterator::rewind(): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/html/moodle/lib/dml/moodle_recordset.php on line 61
PHP Fatal error: Type of xml_format_exception::$line must be int (as in class Exception) in /var/www/html/moodle/lib/xmlize.php on line 42
Fatal error: Type of xml_format_exception::$line must be int (as in class Exception) in /var/www/html/moodle/lib/xmlize.php on line 42
PHP 8.1 では、Moodle 4.1 以降しかインストールできないようです：
https://docs.moodle.org/dev/Moodle_and_PHP