title: append and prepend text to a string
body: <p>I want to be able to search for a certain word in a string, and append and prepend characters to every instance of that word.</p>
  
  <p>example:</p>
  
  <pre><code>I like cats, cats are awesome! I wish I had cats!
  </code></pre>
  
  <p>becomes:</p>
  
  <pre><code>I like (cats), (cats) are awesome! I wish I had (cats)!
  </code></pre>
  
  <p>I know I could use </p>
  
  <pre><code>str_replace( 'cats', '(cats)', $string );
  </code></pre>
  
  <p>but I would have to write "cats" twice.
  I want a method that only requires me to write it once.</p>