html entities function not working

hi everyone i have problem with html entities, this code should work but not, can anyone tell me why?

<?php
$str = "A 'quote' is <b>bold</b>";

// Outputs: A 'quote' is <b>bold</b>
echo htmlentities($str). '<br>';

// Outputs: A 'quote' is <b>bold</b>
echo htmlentities($str, ENT_QUOTES);
?>

When i try this code echo looks like A 'quote' is <b>bold</b> and not like A 'quote' is <b>bold</b>