title: string that matches nth position of substring of array and show value of this array
body: <p>if i have one string is </p>
  
  <pre><code>$str = "CD";
  </code></pre>
  
  <p>than,
  it will found only 3rd and 4th position below array string and fetch that array value,</p>
  
  <pre><code>$arr = ["ABCDE", "BCDEF", "BACDF","ACDLK"];
  </code></pre>
  
  <p>its output will be like below,</p>
  
  <pre><code>$arr = ["ABCDE", "BACDF"];
  </code></pre>
  
  <p>is it possible?</p>