t3lib_div::devLog('Hello world!', 'my_extension', t3lib_div::SYSLOG_SEVERITY_INFO);
$data = array('username' => 'JohnDoe', 'email' => 'johndoe@example.com'); t3lib_div::devLog($data, 'my_extension', t3lib_div::SYSLOG_SEVERITY_DEBUG);This code will output the array $data to the TYPO3 log file with the tag "my_extension" and severity level DEBUG. The t3lib_div devlog utility is part of the TYPO3 core library and can be found in the t3lib/class.t3lib_div.php file.