Calculate reading time for ProcessWire blog/news post

calculate_reading_time.php

<?php // site/ready.php

// Blog/News Post Page - set reading time
$wire->addHookBefore('Pages::saveReady(template=news-post)', function(HookEvent $event) {
	// Get values of arguments sent to hook (and optionally modify them)
	$page = $event->arguments(0);

	// Get the word count of all available text fields that make up the content of the page
	$count['summary_word_count'] = count(wire('sanitizer')->wordsArray(strip_tags($page->summary_textarea)));
	$count['article_word_count'] = count(wire('sanitizer')->wordsArray(strip_tags($page->rte)));
	$total_words = array_sum($count);

	// Set the value for the reading time field (number) based on word count
	// To provide a range, a text value would have to be returned (and stored), but is possible by calculating cpm,
	// wpm_top, wpm_bot and determining variance
	// Source Study: https://iovs.arvojournals.org/article.aspx?articleid=2166061
	$cpm = 987;     // average characters per minute, for English
	$wpm_bot = 161;	// English values for reading speeds
	$wpm_top = 228;
	$wpm_ave = ceil(($wpm_bot + $wpm_top) / 2);
	$page->number_1 = ceil(($total_words) / $wpm_ave);

	// Populate back arguments (assuming they've been modified)
	$event->arguments(0, $page);
});