PHP Write string to new line for the first time and not at the end of file

问题

Using Codeigniter function write_file(), I can write to an existing file like this:

write_file("path_to_file", "String four"."\n", "a+");

Assume I already have a file like this:

String one
String two
String three

With write_file("path_to_file", "String four"."\n", "a+") , I have the ouput below when writing to file for the first time:

String one
String two
String three String four

Any idea about how I can write String four to new line for the first time? Like shown below:

String one
String two
String three 
String four

Thanks.

回答1:

Not knowing much about this write_file() function, but given what you said, this should work :

write_file("path_to_file", "\n"."String four"."\n", "a+")

回答2:

Try adding new line before String four:

write_file("path_to_file", "\nString four\n", "a+")

来源：https://stackoverflow.com/questions/18322558/php-write-string-to-new-line-for-the-first-time-and-not-at-the-end-of-file