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

Question

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

    {
    echo \"\";
}

how

Answer 1

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.