PHP - 文本匹配

I am currently trying to find a percentage of how many words in two strings match

the idea is that you match one string against another and get a % of how similar they are.

what i have at the moment is a rough idea and was wondering if i could get some help the idea is to turned each string into an array you could iterate through the list one by one and adding 1 to $matches if there is a match and 0 if there isn't

<?php>
$originalText = "The quick brown fox jumps over the lazy dog";
$comparisonText = "The quick red fox leaps over the sleeping dog";
//to get a count the number of words we are trying to match
$strNum = str_word_count($originalText);

$arroriginalText = explode(" ", $originalText);
$arrcomparisonText = explode(" ", $comparisonText);

//THIS IS WHERE I'M STUCK
//creating some form of a loop to go through the array of strings

if (preg_match("*word from $arroriginalText*, *word from $arrcomparisonText*", $matches)) {
//not fully understanding what to put here
}

//i'm bad at maths
$strNum - $matches = $percentageFind
$percentageFind / $strNum = $decimal
$decimal * 100 = $theAnswer
?>

I'm not sure if I've made what I'm thinking clear but any help would be much appreciated.

$matches = 0;

if( empty( $arroriginalText ) ) {
  echo 'Empty';
  die();
}

for( $n = 0; $n < count( $arroriginalText ); $n++ ) {
  if( $arrcomparisonText[$n] === $arroriginalText[$n] ) {
     $matches++;
  }
}

$percentage = 100 * $matches / count( $arroriginalText );

or better yet (untested)

$percentage = count( array_diff( $arroriginalText, $arrcomparisonText ) ) / count( $arroriginalText );