title: merge rows in php depened on mysql prev row
body: <p>i've this database table</p>
  
  <pre><code>fromDay - toDay - fromHour-toHour 
  1            1     08:00     14:00
  1            1     15:00     18:00 
  2            2     08:00     18:00 
  </code></pre>
  
  <p>and i want in my html table with the help of php to check if the prev row has 
  the same days then merge this rows into one tr in html table . any ideas how to do it ? </p>