Merge pull request #120 from BuddhikaShaminda/master

add merge sort using php

data_structures/merge sort/merge_sort.php

@@ -0,0 +1,37 @@
+<?php
+function merge_sort($my_array){
+	if(count($my_array) == 1 ) return $my_array;
+	$mid = count($my_array) / 2;
+    $left = array_slice($my_array, 0, $mid);
+    $right = array_slice($my_array, $mid);
+	$left = merge_sort($left);
+	$right = merge_sort($right);
+	return merge($left, $right);
+}
+function merge($left, $right){
+	$res = array();
+	while (count($left) > 0 && count($right) > 0){
+		if($left[0] > $right[0]){
+			$res[] = $right[0];
+			$right = array_slice($right , 1);
+		}else{
+			$res[] = $left[0];
+			$left = array_slice($left, 1);
+		}
+	}
+	while (count($left) > 0){
+		$res[] = $left[0];
+		$left = array_slice($left, 1);
+	}
+	while (count($right) > 0){
+		$res[] = $right[0];
+		$right = array_slice($right, 1);
+	}
+	return $res;
+}
+$test_array = array(100, 54, 7, 2, 5, 4, 1);
+echo "Original Array : ";
+echo implode(', ',$test_array );
+echo "\nSorted Array :";
+echo implode(', ',merge_sort($test_array))."\n";
+?>