include dot(.) and hyphen(-) in a regex

Question

 if(preg_match(\'/[^a-z\\-0-9]/i\', $value))

    {
    echo \"\";
}

how

Answer 1

Assuming you are talking about the regex, you escape both with a slash \.

/[^a-z\.\-0-9]/i

Answer 2

The hyphen does not need to be escaped if it is the last character in the Regex group. But the dot should always be escaped, so

'/[^a-z\.0-9-]/i'

Will check for a to z, . , 0 to 9 and - in that order, case insensitively.

Answer 3

The hyphen doesn't need to be escaped if it's the first or last in the character class.
The dot also doesn't need to escaped when used inside a character class [] i.e.:

/[^a-z.0-9-]/i

---

NOTES:

Apart from the above, the meta characters that also need to be escaped inside a character class are:

^ (negation)
- (range)
] (end of the class)
\ (escape char)

Answer 4

The hyphen is already in there, simply add an escaped dot using \..

/edit: But as noted in the comment the escaping isn't needed.