How to order by a segment of preg_match_all results? - php

Question

I'm using PHP to generate a list of references to a text by doing a preg_match_all search on a database table. Here is the PHP code:
$query = "SELECT primary_tag,display_short_title,content FROM topics;";
$result = mysql_query($query) or die("Query failed : " . mysql_error());
$num_results = mysql_num_rows($result);
for ($i = 0; $i < $num_results; $i++) {
$row = mysql_fetch_array($result);
if (preg_match_all("/(\<i\>U\<\/i\>|U) [0-9]{1,2}\.[0-9]{1,7}/", $row["content"], $matches)) {
foreach ($matches[0] as $match) {
$match = ltrim(strip_tags($match), "U ");
echo '<p class="textmark_result">' . $match;
echo ' ' . $row["display_short_title"] . '';
echo "</p>\n";
}
}
}
And the results (viewing source) look like this:
<p class="textmark_result">15.1737 Medicine</p>
<p class="textmark_result">5.678 Science</p>
<p class="textmark_result">14.665 Science</p>
In the resulting web page, I want to order the results by the decimal in the middle, the $match in the code, so that (in this example) 5.678 comes first, then 14.665, then 15.1737. Is there a way to do that?
Thank you!

Answer 1

Three steps to do:
Get all your matches and add them to an array - floatval($match) is the key.
Sort the resulting array by key (floats sort by numeric value, strings sort by characters - therefore floatval(...)).
Iterate on the sorted array
Code:
// MySQL stuff goes here ...
// create empty array
$results = array();
for ($i = 0; $i < $num_results; $i++) {
$row = mysql_fetch_array($result);
if (preg_match_all("/(\<i\>U\<\/i\>|U) [0-9]{1,2}\.[0-9]{1,7}/", $row["content"], $matches)) {
foreach ($matches[0] as $match) {
$match = ltrim(strip_tags($match), "U ");
// array pseudo key is the float value of $match
// add '_key' member for usort()
$row['_key'] = floatval($match);
$results[] = $row;
}
}
}
// sort the array by the float key
usort($results, function($a, $b) {
if($a['_key'] == $b['_key']) return 0;
elseif($a['_key'] > $b['_key']) return 1;
else return -1;
});
// ... then display stuff in order
foreach($results as $row) {
echo '<p class="textmark_result">' . (string)$row['_key'];
echo ' <a href="../Essays/topic.php?shorttitle='
. $row["primary_tag"] . '">' . $row["display_short_title"] . '</a>';
echo "</p>\n";
}