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Fixing a Small Scripting Problem

Website Automation with PHP and MySQL, Part 6

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Dan Knight - 2002.05.10

This morning I discovered a problem with the PHP scripts we use to display the Mac of the Day and Email List of the Day.

My #2 son Brian <http://brkn.net/> and I came up with the following code to display the Mac of the Day:

<?php
$host = "sqlserver.lowendmac.com";
$username = "MyName";
$password = "MyPassword";
$connection = @mysql_connect($host,$username,$password);
mysql_select_db(lem_mod,$connection);
$today = round((date(U) + 32400) / 86400);
$mod = $today % 89;
$query = mysql_fetch_array(mysql_query("select * from mod where id = '$mod'"));
echo "<B><BR>Mac of the Day</B><BR>&nbsp;<A HREF=/$query[link]>$query[model]</A>";
$lod = $today % 38;
$query = mysql_fetch_array(mysql_query("select * from lists where id = '$lod'"));
echo "<B><BR>List of the Day</B><BR>&nbsp;<A HREF=\"$query[link]\">$query[listname]</A><BR>";
?>

Notice the line near the middle - $mod = $today % 89;

That line tells PHP to use modulo arithmetic to divide today's date (converted to a number) by 89 and discard everything but the remainder. This would give us 89 unique values - just what we need with 89 entries in the Mac of the Day database.

The problem is, modulo arithmetic returns a remainder from 0 (zero) to one less than your maximum number, so our function was using numbers from 0 to 88. And our database uses numbers from 1 to 89.

We use a similar function to handle the 38 email lists, and that's where I noticed the problem this morning. Today the email list script was returning zero, so no list was displayed.

All we have to do is add one to the number returned to have values in the range we need. I've modified two lines, uploaded the new script, and now everything works:

$mod = ($today % 89) + 1;

$lod = ($today % 38) + 1;

The Next Project

I'd planned on automating site links next, but have instead decided that the next project will be automating the Deal of the Day. This will involve real calendar dates, not raw numbers based on seconds since 1970.01.01.

I hope to cover this project next week.

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