Your $string = str_replace("‐"," ",$string);is not using a regular dash character so it does not match
"‐"
versus
"-"
You can see the difference ;-)
Tinker;
>>> $string = "Within 3 days of-death the enzymes-that once-digested your-dinner begin to eat-you.";
=> "Within 3 days of-death the enzymes-that once-digested your-dinner begin to eat-you."
>>> str_replace("-"," ",$string)
=> "Within 3 days of death the enzymes that once digested your dinner begin to eat you."
>>>