What is this code doing?

I came across some sample PHP code, and can’t figure out the syntax. It’s a function that calculates what percentage of a given string is made up of vowels. Ie, “motion” would return a value of [B]50%[/B] (6 letters, of which 3 are vowels. 50%).

[code=php]
function percentVowels_callback($word) {
$word = strtolower($word);
$chars = count_chars($word);
$numVowels = 0;
foreach (array(“a”, “e”, “i”, “o”, “u”) as $vowel) {
$numVowels += $chars[ord($vowel)];
}
return $numVowels / strlen($word);
}
[/code]

Specifically, what is THIS bit:

[code=php] $numVowels += $chars[ord($vowel)];[/code]

Obviously [B]$numVowels[/B] is an integer, and as the loop is being executed, its value keeps increasing, counting the number of vowels in the string. That part I understand. What on earth is [b]$chars[ord($vowel)][/b]?

Remembering that [b]$chars[/b] is an integer, each execution of the loop would look like this:

[code=php]$numVowels += $chars[ord(‘a’)]
$numVowels += $chars[ord(‘e’)]
$numVowels += $chars[ord(‘i’)]
$numVowels += $chars[ord(‘o’)]
$numVowels += $chars[ord(‘u’)][/code]

Let’s say [B]$chars[/B] has a value of 7. Each iteration of the loop now looks like this:

[code=php]$numVowels += 7[ord(‘a’)]
$numVowels += 7[ord(‘e’)]
$numVowels += 7[ord(‘i’)]
$numVowels += 7[ord(‘o’)]
$numVowels += 7[ord(‘u’)][/code]

What on earth is going on? I have never seen PHP code that looks like that.

Also in #PHP _↴