Question

Ive managed to loop through a table and get the difference in days between 2 dates adjacent to each other in the table.

Multiple entries have the same date, i have it now that when that date changes, it displays an image however i want it to display the image as many times as the difference in date

$sql = mysql_query("SELECT * FROM Films_Info") 
 or die(mysql_error()); 

 $last_value = null;

while ($row = mysql_fetch_assoc($sql)) {

  if (!is_null($last_value)) {
  $a = new DateTime($row['FilmRelease']);
  echo "<p>".$row['FilmName']."</p>";
  $interval = $a->diff(new DateTime($last_value));
  //echo $interval->format('%d days');
  $i = 0;

}
$howManydays = $interval->days;

for ( $i; $howManydays; $i++) {
    echo "<img src=\"day.jpg\" />";
    $howManydays = 0;

}

  $last_value = $row['FilmRelease'];
}

Answer 1

for ( $i = 0; $i < $howManydays; $i++) The second is a conditional statement telling when the loop should stop.

The first section in the for loop where it says $i = 0 initialized the variable $i to 0 and then tests the condition $i < $howManydays.

Let’s say $howManydays equals 1. That means 0 < 1, so the loop will perform.

At the end of the loop, the third section is called ($i++), so $i is incremented and now equals 1. The second section is called again to test conditions $i < $howManydays which is asking if 1<1 which it’s not, so the loop will exit.

So if $howManydays is greater than 0, the loop should happen the integer amount that is in $howManydays.

You will want to remove $howManydays = 0; within the for loop, if you don’t want it to only fire once.

The for loop

for ( $i = 0; $i < $howManydays; $i++){
  // ...
}

is somewhat equivalent to the while loop:

$i = 0;
while ( $i < $howManydays ){
  // ...
  $i++;
}

http://php.net/manual/en/control-structures.for.php for more information

In your code above, you should also check if interval was set. You should probably just do an if rather than a while, if only need one interval.