Utf8 BOM Problem

When I recently tested smarty, there was no problem at the beginning. Later I found that CSS errors always occur on the displayed pages. Later I directly output TPL as HTML without any problems, however, once the smarty output is used, an error occurs. No exception is found in the HTML source query, finally, we can't help but use ue to compare the output HTML source and TPL. We found that four spaces are added in front of the page header output by smarty, which is the four leading spaces, I checked the poor information on the Internet and found that it is caused by utf8 BOM problems, because PHP does not support Bom, it does not ignore the three characters at the beginning of the UTF-8-encoded file Bom, it is very easy to solve the problem after finding the problem. Open UE and save the file as UTF without Bom. This simple problem has plagued me for three days.