在php中解码HTML实体无法正常工作

Question

$string = "C-Tru Process Equipments P’ship";
echo html_entity_decode($string);

我希望得到：C-Tru Process Equipments P’ship个结果，但输出为C-Tru Process Equipments P’ship

我将字符串放入https://mothereff.in/html-entities中，这完美地显示了结果，我的字符串文件采用UTF8格式。