PHP syntax error, unexpected $end a cause of errors and _php skills

Parse error:syntax error, unexpected $end in script.php at line xx
After debugging for a while, you find that the row that generated the error is a row in the middle of the file

$str. = ">\n";

I remember. The end tag allowed by the PHP interpreter the line can also be in a single comment, i.e.//$str. = ">\n"; is interpreted as a note before the end tag, and the content of the comment is//$str. = ", and?> behind \ n"; will be interpreted as the contents of the PHP block outside the HTML output! The result is to $str. = ">\n"; This line adds//becomes a comment, instead of a?> end tag, causing the original real end tag to be unexpected (unexpected).
The solution is to simply delete the line.

PHP start and end tag rows don't write anything else, it's a good habit.