auto-read-more.php

<?php

/**
 *
 * @param string $moreLinkText
 * @param integer $stripteaser
 */
function the_content_readmore($moreLinkText = null, $stripteaser = 0)
{
    $content    = apply_filters('the_content', get_the_content($moreLinkText, $stripteaser));
    $paragraphs = explode('</p>', $content);

    // If there's only one paragraph, echo the content and return
    if (2 === count($paragraphs)) {
        echo $content;
        return;
    }
    
    // Always echo first paragraph
    echo $paragraphs[0] . '</p>';
    
    // If the first paragraph has an iframe, also echo second paragraph
    if (false !== stripos($paragraphs[0], '<iframe')) {
        echo $paragraphs[1] . '</p>';
    }

    echo '<a href="javascript:void(0);" class="button button-more">Read More <i class="fa fa-lg fa-chevron-circle-down"></i></a>';
}