Code for completely custom wordpress next and previous buttons

wordpress-next-prev-btns.php

<?php
$prev_post = get_adjacent_post(false,'',true);
$next_post = get_adjacent_post(false,'',false);

if ( !empty( $prev_post ) )
{
    echo '<a href="'.get_permalink($prev_post).'" class="btn arrow-left" title="'.$prev_post->post_title.'" rel="prev">Previous</a>';
}
else
{
    echo '<span class="btn arrow-left disabled">Previous</span>';
}

if ( !empty( $next_post ) )
{
    echo '<a href="'.get_permalink($next_post).'" class="btn arrow-right" title="'.$next_post->post_title.'" rel="next">Next</a>';
}
else
{
    echo '<span class="btn arrow-right disabled">Next</span>';
}
?>