在 PHP 的 str_replace() 中，双反斜杠是什么意思？

Question

I want to remove all \\r \\n \\r\\n which is pretty easy to so I wrote:

str_replace(array("\r","\n"),"",$text);

but I saw this line:

str_replace(array("\r","\n","\\r","\\n"),"",$text);

and I was wondering what is the double backslash means \\\\r and \\\\n .

Answer 1

\\ is an escape character, it's used to escape the following character.

In "\\n" , the backslash escapes n and the result will be a new line character.

In "\\\\n" , the first backslash escapes the second backslash and the n is kept as is, so the result is a string containing \\n (literally).

See the PHP official documentation > Strings .

In the context of your question, str_replace() will remove new lines ( "\\n" and "\\r" ) and also remove \\n and \\r from the string ( "\\\\n" and "\\\\r" respectively). There's no reason a text contains the words \\n and \\r , so it seems that using "\\\\n" and "\\\\r" has no interest here.

Answer 2

The first backslash escapes the second one, so it matches a literal backslash in $text .

I'm not sure why you would want to match that if you just want to remove newlines and carriage returns from the string.