PHP htmlentities only for special chars, not for html tags

PHP htmlentities only for special chars, not for html tags :

If you want to change special char or any maths symbols with html tags to htmlentities without affect the html tags then use the below line of code in php.
 

htmlspecialchars_decode( htmlentities( $str, ENT_NOQUOTES, 'UTF-8', false ), ENT_NOQUOTES );

Example :

<?php
$str = "<b>GvSubhu</b> °";
echo htmlspecialchars_decode( htmlentities( $str, ENT_NOQUOTES, 'UTF-8', false ), ENT_NOQUOTES );
?>

Output :
 

<b>GvSubhu</b> &deg;