Processwire hook to calculate article reading time

calculate_reading_time.php

<?php

/**
 *
 * Calculate reading time on page save.
 * Add this to your ready.php file.
 * Uses a field called 'article_read_time' to store the value
 * and the field 'page_content' as the readable content.
 * You'll need to update those field names if yours are different.
 *
 */

function calculate_reading_time(HookEvent $event) {
    $page = $event->arguments(0);
    
    // If this a post then calculate reading time.
    // You'll need to update this if your template name 
    // is different.
    
    if ($page->template->name == 'post') {

        $page->setOutputFormatting(false);
        
        // strip our tags
        $options=array( "reduceSpace"=> TRUE );
        $article = wire()->sanitizer->textarea($page->page_content, $options);
        $word_count=str_word_count($article);

        $reading_time_secs=($word_count / 265) * 60 ; // medium uses 265 wpm;

        // medium allow 12 secs for the first image and then one sec less
        // for each subsequent image

        $image_count=substr_count($page->page_content, '<img');

        if($image_count>11){
            $image_count=11;
        }

        $image_value=12;
        for($i=1;$i<$image_count;$i++){
            $reading_time_secs+= $image_value;
            $image_value--;
        }

        $reading_time_mins=ceil($reading_time_secs/ 60);

        if($reading_time_mins > 7){ // round up to nearest 5.
            $reading_time_mins=round(($reading_time_mins + 5 / 2 )/5)*5;
        }

        // actually it just looks better as min...
        // $page->article_read_time = $reading_time_mins . ($reading_time_mins>1 ? ' mins' : ' min');
        $page->article_read_time = $reading_time_mins . ' min';
    }
}

wire()->addHookAfter('Pages::saveReady', null, 'calculate_reading_time');