title: putting a backslash before apostrophe
body: <p>Which function processes a string putting a backslash before every apostrophes?
  In other words, I want that  </p>
  
  <pre><code>$string="L'isola";
  echo somefunction($string);
  </code></pre>
  
  <p>returns:</p>
  
  <pre><code>L\'isola
  </code></pre>