htmlentites使用str_replace为img异常输出空字符串

$output = htmlentities($output, ENT_COMPAT, 'UTF-8');
$output = str_replace("&lt;img","<img",$output);

I have a data contain text and image inside of my db,

I need to output it with htmlentites with exception

I tried to use str_replace, somehow, it return empty string after

anyone know where is the problem