How to use backslash in preg_repalce()?

Question

I checked the manual, but I don’t understand this sentence. I would like to ask for advice humbly: If you want to use backslashes in replacement, you must use 4 ("\\\\", translation annotation: because this is first of all a PHP string, After escaping, there are two, and then after passing through the regular expression engine, it is considered to be one original backslash).

Answer 1

Use single quotes directly, why bother?

Answer 2

This is very clear. Two slashes are needed for escaping, one for regular expressions, and one for the original text