Error log on my index file get logged in the error_log.txt file but the same error log is not working in the functions.php file. I am using the latest WordPress and PHP 7.0. I am not using any plugin as well.
error_log("Hello there is an error");
I had a similar problem: calling error_log() from wp-config.php works, but calling it from functions.php does not work for me.
I couldn’t solve this issue but I’ve found a workaround that allowed me to do some sort of debugging at least. I gave up on error_log() and just wrote an own function that logs into a given file:
function mylog($txt) {
file_put_contents('/home/myuser/logs/mylog.txt', $txt.PHP_EOL , FILE_APPEND | LOCK_EX);
}