diff --git a/src/inc/intervals.php b/src/inc/intervals.php
new file mode 100644
index 0000000..10c31f7
--- /dev/null
+++ b/src/inc/intervals.php
@@ -0,0 +1,32 @@
+<?php
+class intervals {
+  public static function wellFormed($i) {
+    return (isset($i[0]) && isset($i[1]) && $i[0] <= $i[1]);
+  }
+
+  public static function measure($i) {
+    return ($i[1] - $i[0]);
+  }
+
+  // Does A overlap B? (with "$open = true" meaning [0, 100] does not overlap [100, 200])
+  public static function overlaps($a, $b, $open = true) {
+    return ($open ? ($a[0] < $b[1] && $a[1] > $b[0]) : ($a[0] <= $b[1] && $a[1] >= $b[0]));
+  }
+
+  // Is A inside of B?
+  public static function isSubset($a, $b) {
+    return ($a[0] >= $b[0] && $a[1] <= $b[1]);
+  }
+
+  // Intersect A and B and return the corresponding interval
+  public static function intersect($a, $b) {
+    $int = [max($a[0], $b[0]), min($a[1], $b[1])];
+
+    return (self::wellFormed($int) ? $int : false);
+  }
+
+  // Return measure of the intersection
+  public static function measureIntersection($a, $b) {
+    return self::measure(self::intersect($a, $b));
+  }
+}