You may use explode() to get it.
$word= "who's'who";
$results= array();
$parts = explode ("'", $word);
foreach ($parts as $part) $results[$part]++;
You then may output like:
foreach ($results as $word => $count) echo $word . " = " . $count. "<br>";
The output should be:
who = 2
s = 1
3
solved How to split and count the words with single quotes (‘)?