$re = '/[^a-zA-Z0-9-]/';
$str = 'my/fancy/thing/test
three.four/now/i/am/two
basic/test
no-slashes
leave_my_underscores_alone
hyphens-and/slashes/and_underscores!plus+random~characters
THE KNIGHTS who say "Ni!"';
$subst = "-";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php