How does PHP obtain a line of data with a carriage return when reading a large file. How can this problem be solved?

How does PHP obtain a line of data with a carriage return when reading a large file. When PHP reads a large file, how does one get a line of data with a carriage return character .??, /R/n is that true? check the php manual fgets-read a row from the file pointer, $ buf = fgets ($ fp ); in $ buf, the read content does not know how to get a line of data with a carriage return when you want PHP to read a large file.
When PHP reads a large file, how does one get a line of data with a carriage return character .??

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/R/n. what do you mean?
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View php Manual

Fgets-read a row from the file pointer
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$ Buf = fgets ($ fp );

$ Buf indicates the read content.

I don't know what you want
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Discussion

$ Buf = fgets ($ fp );
Echo $ buf;

All text content is output.

I want a line in the text.