<?php
if (isset($_GET['text'], $_GET['keys'])) {
$textString = $_GET['text'];
$keysString = $_GET['keys'];

$keyPattern = "/([A-z]*_?)\d+.*\d([A-z]*_?)/";
preg_match_all($keyPattern, $keysString, $keyMatches);

$start = $keyMatches[1][0];
$end = $keyMatches[2][0];

$textPattern = "/$start?[a-z]*(\d+\.?\d+)$end/";
preg_match_all($textPattern, $textString, $textMatches);

$sum = 0;

if (empty($start) || empty($end)) {
echo "<p>A key is missing</p>";
} else {
for ($i = 0; $i < count($textMatches[1]); $i++) {
$sum += $textMatches[1][$i];
}
if ($sum == 0) {
echo "<p>The total value is: <em>nothing</em></p>";
} else {
echo "<p>The total value is: <em>$sum</em></p>";
}
}
}
?>