PHP utf8 half garbled problem

A bug appeared on the website. Garbled characters appeared in the header of the page, but other parts were normal. The header included a head.php, and the entire page was in utf8. But I opened head.php and saw that it was saved in utf8. Copying other normal files and filling in the contents of head.php still doesn't work. Finally, I used linux and vi to create a head.php. I entered the word test and found that the display was normal. So I downloaded head.php, opened it with ue32, and filled in the content. The result page displayed normally. It is probably a problem with the utf8 file header: This normal file does not have EFBB for utf8.

Normal:

Exception: