If you have the situation in mySQL where there is the possibility of large number of connections, you can test for that specific error and then redirect to an different page :
<?php $link = mysql_connect("localhost", "mysql_user",
"mysql_password");
if (mysql_errno() == 1203) {
// 1203 == ER_TOO_MANY_USER_CONNECTIONS (mysqld_error.h)
header("Location: http://your.site.com/alternate_page.php");
exit;
}
?>