Matching - newbie to regular expressions

I want to parse the input from a form so that it only contains upper or lower  letters, numbers and hyphens. How do write such an expression?
if (isset($_POST['frmDomName'])) {
	if ('contains something other that legal l characters') {
		header('Location: http://mydom.com/Failure.php');
	}
}

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cescentmanAsked:
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jet-blackCommented:
Add all charachers that you want:
Like:

if (preg_match('/[A-Za-z0-9]/', $_POST['frmDomName']))
{
                header('Location: http://mydom.com/Failure.php');

}
0
mnialonCommented:
hello,
to match upper or lower  letters, numbers and hyphens, use

if (preg_match('/[A-Za-z\-]/', $_POST['frmDomName']))
0
xBelloxCommented:
This should work fine:

if (isset($_POST['frmDomName'])) {
        if (!ereg("^([0-9]|[a-z]|[A-Z]|_)+$", $_POST['frmDomName'], $reg)) {
                header('Location: http://mydom.com/Failure.php');
        }
}

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0
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jet-blackCommented:
Sorry, I forgot the begining and ending metacharacters:

if (preg_match('/^[A-Za-z0-9\-]*$/', $_POST['frmDomName']))
{
 
}

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cescentmanAuthor Commented:
This work Just fine, but it should be noted that the ! is required for the particular logic I outlined.
if (!preg_match('/^[A-Za-z0-9\-]*$/', $_POST['frmDomName'])) {
	header('Location: http://mydom.com/Failure.php');
}

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0
jet-blackCommented:
cescentman,
Yes, you're right.
0
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