I have the following regex, which I interpret as a pattern that will match a string consisting of just alphanumeric characters and hyphens.
if (preg_match('/[A-Za-z0-9-]/', $subdomain) === false) {
// valid subdomain
}
The problem is this regex is also matching blank spaces, which is obviously undesirable in a subdomain name.
For bonus points, is this a suitable way to validate subdomain names? I'm unsure which special characters are allowed but thought I would keep it simple by only allowing hyphens. Is there anything else I need to check for? For instance a maximum length?
Your pattern matches an ASCII letter or digit or - anywhere inside a string, and if found, returns true. E.g., it will return true if you pass $#$%$&^$g to it.
A pattern that will match a string consisting of just alphanumeric characters and hyphens is
if (preg_match('/^[A-Za-z0-9-]+$/D', $subdomain)) {
// valid subdomain
}
Details:
^ - start of string[A-Za-z0-9-]+ - 1 or more chars that are either ASCII letters, digits or -$ - end of string/D - a PCRE_DOLLAR_ENDONLY modifier that makes the $ anchor match at the very end of the string (excluding the position before the final newline in the string).
