Easy right?

<?php
if($originalPrice > 0) {
	$percentageDrop = intval(100*(($originalPrice - $currentPrice)/$originalPrice));
}
?>

There was a Problem. The prices are stored not as integers but as formatted currency; ie “€ 120,000″

OK – easy – I found a simple solution to strip non alphanumerics (and space) and adapted it slightly:

<?php
function numericFromString( $string )
{
	return preg_replace('/[^0-9]/', '', $string);
}
?>

This function is then applied like so:
$currentPrice = numericFromString( ' € 120,000 ' ) ;

Worked in principle but not in practice – numbers seemed to balloon in size. [I didn't spot it all the numbers which had '8364' at the beginning...]

I had to call in Dave “tech support” Watson. “Bingo!” he said.

The problem [you've figured it out already... ] is that the euro symbol is a numeric HTML entity: €. There’s a bunch of numbers in there too. In fact – 8364.

Pendejo.

So Dave took my adapted [and useless] function and made it work. Now it looks like this:

The Solution

<?php
function numericFromString($string) {
	$string = str_replace('&#8364;','',$string);
	return preg_replace('/[^0-9]/','', html_entity_decode($string));
	}
?>

Why the extra line with str_replace? Because html_entity_decode doesn’t actually decode numerical html entities…

Would you believe it?

For more bullet proof results it may be worthwhile to try the following in place of that str_replace (from the comments at the official PHP manual at php.net)

$string = preg_replace('/&#(\d+);/me',"chr(\\1)",$string); //decimal notation
$string = preg_replace('/&#x([a-f0-9]+);/mei',"chr(0x\\1)",$string);  //hex notation