Shuffling xml output before echoing - php

Question

I have a script that grabs an xml of my database generated by php and I would like to shuffle the rows before the php script echos the xml so that each time i access the database xml file, I'll receive the database in a different order.
here's part of my php script that outputs the xml:
$dom = new DOMDocument("1.0");
$node = $dom->createElement("database");
$parnode = $dom->appendChild($node);
$query = "SELECT * FROM database WHERE 1";
$result = mysql_query($query);
header("Content-type: text/xml");
while ($row = #mysql_fetch_assoc($result)){
// ADD TO XML DOCUMENT NODE
$node = dom->createElement("data");
$newnode = $parnode->appendChild($node);
$newnode->setAttribute("id", $row['id']);
$newnode->setAttribute("name", $row['name']);
$newnode->setAttribute("date", $row['date']);
$newnode->setAttribute("latitude", $row['latitude']);
$newnode->setattribute("longitude", $row['longitude']);
}
This is where I'd like to randomize the xml output if possible. This seems like the most logical place, but if there's a better place, that's fine with me.
echo $dom->saveXML();
Here's a sample of my xml:
<database>
<data id="1" name="blah" date="2012-10-10" latitude="0" longitude="0"/>
<data id="3" name="blah" date="2012-10-10" latitude="0" longitude="0"/>
<data id="4" name="blah" date="2012-10-10" latitude="0" longitude="0"/>
</database>
Simply put, I would like the xml rows to be in a different order each time i access it. Thanks for your help.

Answer 1

One way around this problem is to use a temporary array to store the rows fetched from DB, then shuffle this array, then walk through it:
$records = array();
while ($row = #mysql_fetch_assoc($result)){
$records[] = $row;
}
shuffle($records);
foreach ($records as $row) {
$node = dom->createElement("data");
$newnode = $parnode->appendChild($node);
$newnode->setAttribute("id", $row['id']);
...
}
The other way is use the original array as it is, but randomize the insertion process instead:
$prevnode = null;
while ($row = #mysql_fetch_assoc($result)){
$node = dom->createElement("data");
if ($prevnode && rand(0, 1) === 0) {
$newnode = $prevnode->insertBefore($node);
} else {
$newnode = $parnode->appendChild($node);
}
$prevnode = $newnode;
$newnode->setAttribute("id", $row['id']);
...
}

Answer 2

If your result set is not very large and your database supports it, you can have the database shuffle the results for you. For example, MySQL can do this:
SELECT * FROM database ORDER BY rand();
Your database may differ.
You could also separate XML generation from result collection. Shuffle the intermediate array:
function get_database_results($dbconn=null) {
$rows = false;
$query = 'SELECT * FROM database';
$res = mysql_query($query, $dbconn);
if ($res) {
$rows = array();
while ($row = mysql_fetch_assoc($res)) {
$rows[] = $row;
}
}
return $rows;
}
function array_to_sxe($rows) {
$sxe = simplexml_load_string('<database></database>');
foreach ($rows as $row) {
$data = $sxe->addChild('data');
foreach ($row as $key => $value) {
$data->addAttribute($key, $value);
}
}
return $sxe;
}
$rows = get_database_results();
shuffle($rows);
$sxe = array_to_sxe($rows);
header('Content-Type: application/xml'); // NOT text/xml!
echo $sxe->asXML();
I will now rant about encodings.
You have to be more careful about your encodings! As it is, you can very easily generate malformed XML.
text/xml means that the xml is in 7-bit ascii. That is very unlikely what you meant.
application/xml means that the xml is utf-8. This is what DOMDocument and SimpleXML output by default, and only accept utf-8 values for methods like setAttribute! This means you need to be absolutely sure:
That the strings you put into the database are utf-8.
That the connection between php and the database is utf-8. (Using SET NAMES utf8 or the charset parameter to the DSN with PDO--which you should be using instead of mysql_*)
That the strings you pull out of the database are utf-8, or at least are converted to utf-8 before use.

Answer 3

You can add
ORDER BY rand()
to your SQL-Query