Tip : Validating age and Date of birth

Every now and then you come across the need to gather date of birth information from users and to validate their age against the minimum required age to access the website, here's the code which will help you do that, we'll collect the dob information in the following format YYYY-MM-DD using an input form control :

 function valid_age($dob, $age)
 {
   $today = getdate();
   
   if($today['year'] < $dob['year'])
   {
     return false;
   }
   else
   {
     if($today['mon'] > $dob['mon'])
     {
       if(($today['year'] - $dob['year']) >= $age)
       {
         return true;
       }
       else
       {
         return false;
       }
     }
     else if($today['mon'] > $dob['mon'])
     {
       if(($today['year'] - $dob['year'] - 1) >= $age)
       {
         return true;
       }
       else
       {
         return false;
       }
     }
     else
     {
       if($today['mday'] > $dob['mday'])
       {
         if(($today['year'] - $dob['year']) >= $age)
         {
           return true;
         }
         else
         {
           return false;
         }
       } 
       else if($today['mday'] < $dob['mday'])
       {
         if(($today['year'] - $dob['year'] - 1) >= $age)
         {
           return true;
         }
         else
         {
           return false;
         }
       }
       else
       {
         if(($today['year'] - $dob['year']) >= $age)
         {
           return true;
         }
         else
         {
           return false;
         }
       }
     }
   }  
 }
 
 $_POST['dob'] = trim($_POST['dob']);
 if(!preg_match('/(\d{4})\-(\d{1,2})\-(\d{1,2})/', $_POST['dob'], $dob_comps))
 {
   $show_error  = 1;
 }
 else if(!checkdate($dob_comps[2], $dob_comps[3], $dob_comps[1]))
 {
   $show_error = 1;
 }
 else if  (!valid_age(array('mon' => $dob_comps[2], 'mday' => $dob_comps[3], 'year' => $dob_comps[1]), 13))
 {
   $show_error = 1;
 }
 else
 {
   $clean_data['dob'] = $_POST['dob']; 
 }

Try figuring out how this code works on you, if you can't understand on your own then don't worry i'll explain it in my next post.