title: Echo previous and next number with decimal
body: <p>I am building a manga page with PHP.
  My chapter rows in SQL have </p>
  
  <pre><code> id int(11) unsigned NOT NULL auto_increment,
   catid smallint(5) unsigned NOT NULL default '0',
   listcatid varchar(255) NOT NULL default '',
   topicid smallint(5) unsigned NOT NULL default '0',
   admin_id mediumint(8) unsigned NOT NULL default '0',
   author varchar(255) default '',
   sourceid mediumint(8) NOT NULL default '0',
   addtime int(11) unsigned NOT NULL default '0',
   edittime int(11) unsigned NOT NULL default '0',
   status tinyint(4) NOT NULL default '1',
   publtime int(11) unsigned NOT NULL default '0',
   exptime int(11) unsigned NOT NULL default '0',
   archive tinyint(1) unsigned NOT NULL default '0',
   title varchar(255) NOT NULL default '',
   alias varchar(255) NOT NULL default '',
   chapter float default '0',
  </code></pre>
  
  <p>I try to show a Next Chapter and Previous Chapter each detailed chapter.
  But the chapter not step by step.</p>
  
  <p>In example, I want if visitor watch at chapter 10 and in Database have chapter 9, 9.5, 10.5, 10. They can be echo as Previous Chapter and Next Chapter.</p>
  
  <p>If I am watching chapter 10 and use "SELECT chapter WHERE chapter= chapter+1" as the Next Chapter, the next chapter will be 11. They skiped the chapter with decimal, in my example is 10.5.</p>
  
  <p>This is a demo link
  <a href="http://truyentranhtuan.com/onepunch-man-chuong-48-5/" rel="nofollow">http://truyentranhtuan.com/onepunch-man-chuong-48-5/</a></p>
  
  <p>You can see the left and right arrow. I just want to echo a result like that. </p>
  
  <p>Is there any solution ? </p>