Update README.md

Author: dan-on

README.md

@@ -1,2 +1,36 @@
 # PHP Interval tree
-Is an implementation of interval binary search tree according to Thomas H. Cormen book "Introduction to Algorithms".
+Is an implementation of interval binary search tree according to Thomas H. Cormen book "Introduction to Algorithms".
+
+## Usage
+
+```php
+<?php
+require_once 'vendor/autoload.php';
+
+use Danon\IntervalTree\IntervalTree;
+
+$tree = new IntervalTree();
+$intervals = [[6,8],[1,4],[2,3],[5,12],[1,1],[3,5],[5,7]];
+
+// Insert interval as a key and string "val0", "val1" etc. as a value 
+for ($i=0; $i < count($intervals); $i++) {
+    $tree->insert($intervals[$i], "val" . $i);
+}
+
+// Get array of keys sorted in ascendant order
+$sorted_intervals = $tree->getKeys(); //  expected array [[1,1],[1,4],[5,7],[5,12],[6,8]]
+
+// Search items which keys intersect with given interval, and return array of values
+$valuesInRange = $tree->search([2,3], function($value, $key) {
+    return $value;
+});
+
+print_r($valuesInRange);
+
+// Array
+// (
+//     [0] => val1
+//     [1] => val2
+//     [2] => val5
+// )
+```