title: compare two text files via php but find diffrence
body: <p>I have 2 text files</p>
  
  <p><strong>a.txt</strong></p>
  
  <pre><code>1111
  2222
  3333
  4444
  5555
  </code></pre>
  
  <p><strong>b.txt</strong></p>
  
  <pre><code>6666
  1111
  7777
  8888
  2222
  9999
  </code></pre>
  
  <p>I am running this script</p>
  
  <pre><code>$lines1 = file("a.txt");
  $data2 = file_get_contents("b.txt");
  
  foreach($lines1 as $line1){
  $line1 = trim($line1);
  
  if(strpos($data2, $line1)){
  echo $line1;
  echo "&lt;br /&gt;";
  }
  }
  </code></pre>
  
  <p>code working it list all lines from a.txt which are available in b.txt</p>
  
  <p>but i need inverse of this code.I want it shows only that is not available on b.tx</p>