convert a string into its html entitles using php htmlentities function

PHP

$string = "<a href='#i_am_the_link_target'>Im a Link text</a>.";
$string_htmlentities = htmlentities($string);
echo "<h3>The original String</h3>";
echo $string;
echo "<h3>The String after being converted</h3>";
echo $string_htmlentities;
echo "<p>if you want to see the encoded characters you can always add it to a text areas.</p>";
echo "<textarea>$string_htmlentities</textarea>";
echo "<p>you can also decode the entities with the following function<p>";
$string_htmlentities_decode = html_entity_decode($string_htmlentities);
echo $string_htmlentities_decode;
echo "<textarea>$string_htmlentities_decode</textarea>";
echo htmlspecialchars($string);
  echo "<textarea>";
echo htmlspecialchars($string);
echo "</textarea>";
echo "<p>actually the one i was looking for here was htmlspecialchars_decode got there in the end!</p>";
echo htmlspecialchars_decode($string);
echo "<textarea>";
echo htmlspecialchars_decode($string);
echo "</textarea>";

echo htmlspecialchars($string, ENT_QUOTES, 'UTF-8');