PHP prints out HTML instead of processing the HTML - php

Question

I hope someone can help me with this. The code below is from a WordPress Plugin. From the plugin option page I am entering some simple html -
<h3>Showname</h3><p>with DJ Top</p>
The code below ($showname) is used (a WordPress shortcode) to display what I've entered, but it actually displays the HTML rather than processing it i.e displaying the HTML header and paragraph.
Can anyone point me in the direction so $showname processes the HTML rather than just printing it out verbatim tags and all.
Many thanks
Rob
function showtime_schedule_handler($atts, $content=null, $code=""){
global $wpdb;
global $showtimeTable;
//Get the current schedule, divided into days
$daysOfTheWeek = array("Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday");
$schedule = array();
$output = '';
foreach ($daysOfTheWeek as $day) {
//Add this day's shows HTML to the $output array
$showsForThisDay = $wpdb->get_results( $wpdb->prepare ( "SELECT * FROM $showtimeTable WHERE dayOfTheWeek = '$day' ORDER BY startTime" ));
//Check to make sure this day has shows before saving the header
if ($showsForThisDay){
$output .= '<h2>'.$day.'</h2>';
$output .= '<ul class="showtime-schedule">';
foreach ($showsForThisDay as $show){
$showName = $show->showName;
$startClock = $show->startClock;
$endClock = $show->endClock;
$linkURL = $show->linkURL;
if ($linkURL){
$showName = ''.$showName.'';
}
$output .= '<li><strong>'.$startClock.'</strong> - <strong>'.$endClock.'</strong>: '.$showName.'</li>';
}
$output .= '</ul>';
}
}
return $output;
}

Answer 1

You're outputting with a variant of the text/plain MIME type. You'll need to send it out with a default header (text/html) in order for the browser to parse it properly.
For instance:
<?php
header('Content-Type: text/html', true);
echo showtime_schedule_handler($atts, $content);
?>

Answer 2

Instead of
return $output;
try
return html_entity_decode($output);