Questions about carriage return when php writes a text file

The question about the carriage return when php writes a text file is found today when writing a log file, the written content does not wrap. I checked some information to find some problems .? The related code is as follows :? File_put_contents ($ _ SESSION [projectname], the balance sheet is successfully written into rn, FILE_APPEND );? Or? Why fpfopen(log.txt about carriage return when php writes a text file

When writing a log file today, it is found that the written content will not wrap. I checked some information to find some problems.

?

The related code is as follows:

?

File_put_contents ($ _ SESSION ['projectname'], 'balance sheet written successfully \ r \ n', FILE_APPEND );

?

Or

?

$ Fp = fopen('log.txt ', 'A'); fwrite ($ fp, 'balance sheet written successfully \ r \ ntest'); fclose ($ fp );

?

The code is correct, but \ r \ n will be output directly after the file is written, rather than press Enter.

?

However, in windows, \ r \ n does mean a carriage return, and there is no error. after a while,

?

Later, I changed the string-enclosed quotation marks from single quotation marks to double quotation marks, and everything was OK.

?

Seemingly small differences, but the results are indeed unexpected.

?

Although I don't know why, keep a record

?