Using for loop to speed up PHP code typing

Question

Hi everyone I've been extracting rows from a SQL table 1 by 1. I wrote this code two years ago and realise how hideously ineffective it is. I'd like to speed things up by typing up a simple for-loop to automate the coding.

$maxRows_dd1 = 10;
$pageNum_dd1 = 0;
if (isset($_GET['pageNum_dd1'])) {
  $pageNum_dd1 = $_GET['pageNum_dd1'];
}
$startRow_dd1 = $pageNum_dd1 * $maxRows_dd1;

$maxRows_dd2 = 10;
$pageNum_dd2 = 1;
if (isset($_GET['pageNum_dd2'])) {
  $pageNum_dd2 = $_GET['pageNum_dd2'];
}
$startRow_dd2 = $pageNum_dd2 * $maxRows_dd2;

$maxRows_dd3 = 10;
$pageNum_dd3 = 2;
if (isset($_GET['pageNum_dd3'])) {
  $pageNum_dd3 = $_GET['pageNum_dd3'];
}
$startRow_dd3 = $pageNum_dd3 * $maxRows_dd3;

... dd4 to dd99 go in between!

$maxRows_dd100 = 10;
$pageNum_dd100 = 99;
if (isset($_GET['pageNum_dd99'])) {
  $pageNum_dd32 = $_GET['pageNum_dd99'];
}
$startRow_dd99 = $pageNum_dd99 * $maxRows_dd99;

which corresponds to:

mysql_select_db($database_rent, $rent);
$query_dd1 = "SELECT * FROM rent";
$query_limit_dd1 = sprintf("%s LIMIT %d, %d", $query_dd1, $startRow_dd1, $maxRows_dd1);
$dd1 = mysql_query($query_limit_dd1, $rent) or die(mysql_error());
$row_dd1 = mysql_fetch_assoc($dd1);

if (isset($_GET['totalRows_dd1'])) {
  $totalRows_dd1 = $_GET['totalRows_dd1'];
} else {
  $all_dd1 = mysql_query($query_dd1);
  $totalRows_dd1 = mysql_num_rows($all_dd1);
}
$totalPages_dd1 = ceil($totalRows_dd1/$maxRows_dd1)-1;

mysql_select_db($database_rent, $rent);
$query_dd2 = "SELECT * FROM rent";
$query_limit_dd2 = sprintf("%s LIMIT %d, %d", $query_dd2, $startRow_dd2, $maxRows_dd2);
$dd2 = mysql_query($query_limit_dd2, $rent) or die(mysql_error());
$row_dd2 = mysql_fetch_assoc($dd2);

if (isset($_GET['totalRows_dd2'])) {
  $totalRows_dd2 = $_GET['totalRows_dd2'];
} else {
  $all_dd2 = mysql_query($query_dd2);
  $totalRows_dd2 = mysql_num_rows($all_dd2);
}
$totalPages_dd2 = ceil($totalRows_dd2/$maxRows_dd2)-1;

mysql_select_db($database_rent, $rent);
$query_dd3 = "SELECT * FROM rent";
$query_limit_dd3 = sprintf("%s LIMIT %d, %d", $query_dd3, $startRow_dd3, $maxRows_dd3);
$dd3 = mysql_query($query_limit_dd3, $rent) or die(mysql_error());
$row_dd3 = mysql_fetch_assoc($dd3);

if (isset($_GET['totalRows_dd3'])) {
  $totalRows_dd3 = $_GET['totalRows_dd3'];
} else {
  $all_dd3 = mysql_query($query_dd3);
  $totalRows_dd3 = mysql_num_rows($all_dd3);
}
$totalPages_dd3 = ceil($totalRows_dd3/$maxRows_dd3)-1;

... all the way to dd100!!!

How would I use a for loop to speed typing up all this code for each block of code from dd1 to dd100?

My manager asked me to update his system and I've just realised how much time I would waste trying to add 100 instances of dd! — methuselah
– methuselah, Commented Dec 27, 2011 at 17:45
What are you actually doing with this data that you have retrieved from the database? Displaying it on a page or something else? And why do you need these in separate results? Can't you just query the database once? — DaveRandom
– DaveRandom, Commented Dec 27, 2011 at 17:46
@DaveRandom - the data is displayed row by row on a table. Each row can hold only 10 values from the table. — methuselah
– methuselah, Commented Dec 27, 2011 at 18:37
@methuselah can you show the code you use for generating the table? — DaveRandom
– DaveRandom, Commented Dec 27, 2011 at 19:50

Álvaro González · Accepted Answer · 2011-12-27 17:47:02Z

3

Read about arrays and for() loops.

answered Dec 27, 2011 at 17:47

Álvaro González

147k45 gold badges282 silver badges378 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

DaveRandom · Accepted Answer · 2011-12-28 13:48:15Z

This is a much more efficient code to do exactly what you do above:

<?php

  // You only need to do these once as they are the same throughout
  mysql_select_db($database_rent, $rent);
  $maxRows = 10;
  // This code gets the total number of rows in the database
  $totalRowsAll = mysql_fetch_assoc(mysql_query("SELECT count(*) AS total FROM rent", $rent));
  $totalRowsAll = (int) $totalRowsAll['total'];

?>
<div class="tab_container">
    <div id="tab1" class="tab_content">
      <table width="100%" border="0" cellspacing="5" cellpadding="5" id="1">
<?php

  for ($i = 0; $i < 100; $i++) {

    // Calcluate value for this iteration and query database
    $pageNum = (isset($_GET['pageNum_dd'.($i + 1)])) ? (int) $_GET['pageNum_dd'.($i + 1)] : $i;
    $startRow = $pageNum * $maxRows;
    $query = "SELECT * FROM rent LIMIT $startRow, $maxRows";
    $result = mysql_query($query, $rent) or die(mysql_error($rent));
    $totalRows = (isset($_GET['totalRows_dd1'])) ? (int) $_GET['totalRows_dd1'] : $totalRowsAll;
    ${'totalPages_dd'.($i + 1)} = ceil($totalRows / $maxRows) - 1;

    // Now print this row
?>
        <tr height="100px" align="center">
<?php

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

?>

            <td style="background-color: <?php echo $row['colour']; ?>;" onclick="window.location='pay.php?id=<?php echo $row['dNo']; ?>&user=<?php echo $username; ?>'" onmouseover="this.style.cursor='pointer'"> 
              <form action="pay.php?id=<?php echo $row['dNo']; ?>&user=<?php echo $username; ?>" method="post">
                <input type="hidden" id="<?php echo $row['dNo']; ?>">
                <input type="hidden" value="<?php echo $username; ?>">
                <button type="submit" class="link" id="t<?php echo $row['dNo']; ?>">
                  <span><?php echo $row['dNo']; ?></span>
                </button>
              </form>
            </td>
<?php

    } // End while

?>
        </tr>
<?php

  } // End for

?>
      </table>
    </div>
</div>

...however:

I'm fairly sure this could be summed up in a single query to get all the results you need, which would be much more efficient and drastically reduce database load. But because of the $_GET['pageNum_dd*'] and $_GET['totalPages_dd*'] variables which are used on a per row basis, I am not 100% sure about this, and I can't work out how this would be done without knowing more about what is produced. You need to examine whether or not these parameters that can be passed are actually necessary/useful. As it is, they may be cause rows of a varying length, with an unequal number of cells per row - which is probably not what you want.

The same also goes for the variables $totalPages_dd*, which are assigned below but never used anywhere. They may not be useful, and assigning them may be pointless.

Hey thanks for the help - I've got 20 tabs i.e. <div id="tab1" class="tab_content"></div> each with 10 by 5 rows - will the code be able to output that? Here's an image of how it should look like (but going all the way to 951-1000) - i.imgur.com/JXM0d.jpg

Collectives™ on Stack Overflow

Using for loop to speed up PHP code typing

2 Answers 2

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related