not understanding preg_replace

[helloise]

i am reading the php manual but what are all those characters for?

ex:

$msg 			= preg_replace("/[^A-z0-9]/"," ",$msg);

what does the / [ ^ mean??

here is another one:

function checkPhone($number)
{
    if(preg_match('^[0-9]{3}+-[0-9]{3}+-[0-9]{4}^', $number)){
        return $number;
    } else {
        $items = Array('/\ /', '/\+/', '/\-/', '/\./', '/\,/', '/\(/', '/\)/', '/[a-zA-Z]/');
        $clean = preg_replace($items, '', $number);
        return substr($clean, 0, 3).'-'.substr($clean, 3, 3).'-'.substr($clean, 6, 4);
    }
}

what on earth does

$items = Array('/\ /', '/\+/', '/\-/', '/\./', '/\,/', '/\(/', '/\)/', '/[a-zA-Z]/');

mean??
and the { + - in preg_match('^{[0-9]{3}+-[0-9]{3}+-[0-9]{4}}

thank you

[laserlight]

You should read the PHP manual on PCRE.

[bradgrafelman]

And here is another excellent resource on regular expressions.