preg_quote() takes str and puts a backslash in front of
every character that is part of the regular expression
syntax. This is useful if you have a run-time string that you
need to match in some text and the string may contain special
regex characters.
If the optional
delimiter is specified, it will also be escaped.
This is useful for escaping the delimiter that is required by
the PCRE functions. The / is the most commonly used
delimiter.
The special regular expression characters are:
. \\ + * ? [ ^ ] $ ( ) { } = ! | : |