function.php create Fatal error: Cannot redeclare attitude_constants()

Thanks
i do the same ,create blank function.phpin child theme and add a followin code `<?php

// Remove old copyright text
add_action( 'init' , 'mh_remove_copy' , 15 );
function mh_remove_copy() {
        remove_action( 'attitude_footer', 'attitude_footer_info', 30 );
}

// Add my own copyright text
add_action( 'attitude_footer' , 'mh_footer_info' , 30 );
function mh_footer_info() {
   $output = '<div class="copyright">'.'Copyright © [the-year] [site-link] Powered by: SUPER MARTIANS FROM MARS! '.'</div><!-- .copyright -->';
   echo do_shortcode( $output );
}
?>

to remove credit from the theme ,iam using attitude theme and follow the below post.

http://wordpress.org/support/topic/remove-or-edit-info-in-footer?replies=28

but this will change nothing or doesnot work.

thanks