// Convert decimal
$source = preg_replace('/&#(\d+);/me', "utf8_encode(chr(\\1))", $source); // decimal notation
// Convert hex
$source = preg_replace('/&#x([a-f0-9]+);/mie', "utf8_encode(chr(0x\\1))", $source); // hex notation

// Convert decimal
$source = preg_replace('/&#(\d+);/m', "utf8_encode(chr(\\1))", $source); // decimal notation
// Convert hex
$source = preg_replace('/&#x([a-f0-9]+);/mi', "utf8_encode(chr(0x\\1))", $source); // hex notation