title: How to convert some multibyte characters into its numeric html entity using PHP?
body: <p>Test string:</p>
  
  <pre><code>$s = "convert this: ";
  $s .= "–, —, †, ‡, •, ≤, ≥, μ, ₪, ©, ® y ™, ⅓, ⅔, ⅛, ⅜, ⅝, ⅞, ™, Ω, ℮, ∑, ⌂, ♀, ♂ ";
  $s .= "but, not convert ordinary characters to entities";
  </code></pre>