PHP is very slow when printing a large amount of information

Question

I have an application where I need to retrieve a large amount of rows from the database and then print them all on the screen. I've checked the mysql queries, and that's not where the problem is. The problem is the rows all need to be printed on the same page, with no pagination, and it takes a long time (I'm talking about a table with several thoudands of rows). Is there any way to speed things up? The only thing I've found on Google is using "," instead of "." when using echo. I'll be testing this to see if there is any improvement, but I'm not sure it will make such a big difference.

Answer 1

The problem is unlikely PHP, it's the massive amount of HTML being output to the browser. You could verify this yourself by saving the page that you get, then loading the static file from your hard drive.

If you are outputting a large table, then the browser will often have problems with "redrawing" it as content is loaded. This can be minimized by setting a fixed width for all the columns. Just do this on the first row.

You can also jump out of the PHP block to output most of the HTML, then just print the variables where appropriate. Here's an example, assuming all your data is in the $rows variable:

<?php
  // some code here
?>

<table>
<thead>
<tr>
  <th width="50">Header 1</th>
  <th width="200">Header 2</th>
  <th width="150">Header 3</th>
  <th width="100">Header 4</th>
</tr>
</thead>
<tbody>
<?php foreach ( $rows as $r ) : ?>
<tr>
  <td><?=$r['var1']?><td>
  <td><?=$r['var2']?><td>
  <td><?=$r['var3']?><td>
  <td><?=$r['var4']?><td>
</tr>
<?php endforeach; ?>
</tbody>
</table>

<?php
  // continue here if necessary

Note: if you don't have PHP short tags enabled you'll need to do <?php echo $r['var1'] ?> instead.

Finally, you can try adding gzip compression. It's best done at a server level but in PHP you can do add the line ob_start("ob_gzhandler"); as the very first line of PHP code right after <?php.

If this still does not help, then it's a simple fact that your table is way too big. You'd be much better off using pagination or filtering to keep the size down.

Answer 2

PHP is not your bottleneck. Here is a presentation that I've attended about PHP performance by Rasmus Lerdorf, the guy who created PHP. PHP is one of the last things that you have to worry in terms of performance. You can print millions of row entries and do complex calculations without problem. Before throwing it to PHP check your code, your queries, your webserver settings.

As Mark suggested you can use flush to send output to browser while still getting information from db.