how to add the node in array after declaration code example

Example 1: get the string after a character in php

$data = "123_String";    
$whatIWant = substr($data, strpos($data, "_") + 1);    
echo $whatIWant;

Example 2: how to get the last element in an array in c#

using System;

public class Demo {
   public static void Main() {
      string[] str = new string[] {
         "Java",
         "HTML",
         "jQuery",
         "JavaScript",
         "Bootstrap"
      };
      Console.WriteLine("Array...");
      foreach(string res in str) {
         Console.WriteLine(res);
      }
      Console.WriteLine("Last element: "+str[str.Length - 1]);
   }
}