title: How to remove duplicate words from string using php?
body: <p>Below is the variable I have, </p>
  
  <pre><code>$string = 'AAA,BBB,aAA,BbB,AAA,BbB';
  </code></pre>
  
  <p>I need the unique string result below,</p>
  
  <pre><code>$string = 'AAA,BBB,aAA,BbB';
  </code></pre>
  
  <p>How to make it unique just like <code>array_unique()</code> function , is there any default String function to remove duplicate string in PHP?</p>