diff --git a/leap.php b/leap.php
new file mode 100644
index 0000000..e6585a7
--- /dev/null
+++ b/leap.php
@@ -0,0 +1,17 @@
+<?php
+function isLeap($year)
+{
+	return by400($year) or (by4($year) and notBy100($year));
+}
+function by4($number)
+{
+	return $number % 4 == 0;
+}
+function notBy100($number)
+{
+	return $number % 100 != 0;
+}
+function by400($number)
+{
+	return $number % 400 == 0;
+}