The default SearchWP Regex Whitelist

gistfile1.php

<?php

// THE DEFAULT SEARCHWP REGEX WHITELIST

private $term_pattern_whitelist = array(

	// these should go from most strict to most loose

	// functions
	"/(\\w+?)?\\(|[\\s\\n]\\(/is",

	// Date formats
	"/([0-9]{4}-[0-9]{1,2}-[0-9]{1,2})/is",       // date: YYYY-MM-DD
	"/([0-9]{1,2}-[0-9]{1,2}-[0-9]{4})/is",       // date: MM-DD-YYYY
	"/([0-9]{4}\\/[0-9]{1,2}\\/[0-9]{1,2})/is",   // date: YYYY/MM/DD
	"/([0-9]{1,2}\\/[0-9]{1,2}\\/[0-9]{4})/is",   // date: MM/DD/YYYY

	// IP
	"/(\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3})/is",    // IPv4

	// initials
	"/\\b((?:[A-Za-z]\\.\\s{0,1})+)/isu",

	// version numbers: 1.0 or 1.0.4 or 1.0.5b1
	"/([a-z0-9]+(?:\\.[a-z0-9]+)+)/is",

	// serial numbers
	"/(\\b[-_]?[0-9a-zA-Z]+(?:[-_]+[0-9a-zA-Z]+)+[-_]?)/isu",  // hyphen/underscore separator

	// strings of digits
	"/\\b(\\d{1,})\\b/is",

	// e.g. M&M, M & M
	"/\\b([[:alnum:]]+\\s?(?:&\\s?[[:alnum:]]+)+)/isu",

);

They are escaped backslashes e.g. https://regex101.com/r/tDjIzy/1

I looked up this file in the actual WordPress plugin, it doesn't use escaped backslashes, it's actually just using the code \b which is for any word boundary character. This gist isn't really accurate compared to the source file in the WP plugin.

In any case, no big deal. I just was trying to make my own pattern and couldn't figure out why anybody would ever type "\b" into a search bar, or why that would be in the pattern in the first place. And it's not, this is just representing a word boundary, it's not supposed to be two backslashes, just one.