Try this...

Cheers,
Justin.

----

	$test_array =   array
					(
					"623456-gdfgdfgdfgfd",
					"623456-54treeg",
					"123-fdsOPOPPO",
					"947386-gdfgdfgdfgfd",
					"   623456-gdfgdfgdfgfd"
					);

	foreach ( $test_array as $str )
	{

		if ( preg_match("/^([0-9]{6}-.*)/",$str) )
		{
			echo "<b>Valid:</b> '$str'";
		}
		else
		{
			echo "<b>Not Valid:</b> '$str'";	
		}
		
		echo "<p>";
	}