Added merge-sort Algoritm in PHP

PHP/merge-sort.php

@@ -0,0 +1,67 @@
+<?php
+    // --------------- Merge Sort Algo ----------------------
+    function mergesort(&$arr, $left, $right) {
+        if ($left < $right) { 
+            $mid = $left + (int)(($right - $left)/2);
+            mergesort($arr, $left, $mid);
+            mergesort($arr, $mid+1, $right);
+            merge($arr, $left, $mid, $right);
+        }
+    }
+
+    // This function merges the arrays
+    function merge(&$arr, $left, $mid, $right) {
+
+        $n1 = $mid - $left + 1; //LeftArray size
+        $n2 = $right - $mid;     //RightArray size
+
+        $LeftArray = array_fill(0, $n1, 0); 
+        $RightArray = array_fill(0, $n2, 0);
+
+        for($i=0; $i < $n1; $i++) { 
+            $LeftArray[$i] = $arr[$left + $i];
+        }
+        for($i=0; $i < $n2; $i++) { 
+            $RightArray[$i] = $arr[$mid + $i + 1];
+        }
+
+
+        $l=0; $r=0; $i=$left;
+        while($l < $n1 && $r < $n2) {
+            if($LeftArray[$l] < $RightArray[$r]) { 
+                $arr[$i] = $LeftArray[$l]; 
+                $l++; 
+            }
+            else { 
+                $arr[$i] = $RightArray[$r];  
+                $r++; 
+            }
+            $i++;
+        }
+
+        while($l < $n1) { 
+            $arr[$i] = $LeftArray[$l];  
+            $l++;  
+            $i++;
+        }
+
+        while($r < $n2) { 
+            $arr[$i] = $RightArray[$r]; 
+            $r++;  
+            $i++; 
+        }
+    }
+
+
+
+    // --------------- Calling the function with array-------------
+
+    $MyArray = array(100, 23, -10, 8, 0, 188, 928, 19, 989, 9, 1002);
+    $n = sizeof($MyArray); 
+    echo "Array:\n";
+    print_r($MyArray);
+
+    mergesort($MyArray, 0, $n-1);
+    echo "Array After sorting:\n";
+    print_r($MyArray);
+?>