Theme Switcher Error

I recently installed the WP Theme Switcher plugin and it went well, not a problem.

However I went to switch themes on my site the next day and I got these error messages:

Warning: Cannot modify header information – headers already sent by (output started at /home/pretsorg/public_html/eclipse/index.php:2) in /home/pretsorg/public_html/eclipse/wp-content/plugins/theme-switcher.php on line 37

Warning: Cannot modify header information – headers already sent by (output started at /home/pretsorg/public_html/eclipse/index.php:2) in /home/pretsorg/public_html/eclipse/wp-content/plugins/theme-switcher.php on line 44

I’m not sure what is causing these errors and I’ve reinstalled the plugin several times. I also tried setting the name of my themes and the folder they’re in to the same name, and also deleting spaces in the theme name.

Someone told me that whitespace might be the problem, but I’m rather clueless as to what this is.

Any help would be greatly appreciated.
Also, my site is https://prettyskies.org/eclipse
The error I get is on this page: https://prettyskies.org/eclipse/index.php?wptheme=Supernatural+Patience

And this is the actual theme switcher plugin that I’m using:

<?php

/*
Plugin Name: Theme Switcher
Plugin URI: https://www.ads-software.com/
Description: Allow your readers to switch themes.
Version: 0.5
Author: Ryan Boren
Author URI: https://boren.nu/

Adapted from Alex King’s style switcher.
https://www.alexking.org/software/wordpress/

To use, add the following to your sidebar menu:

• Themes:
  <?php wp_theme_switcher(); ?>

This will create a list of themes for your readers to select.

If you would like a dropdown box rather than a list, add this:

• Themes:
  <?php wp_theme_switcher(‘dropdown’); ?>

*/

function ts_set_theme_cookie() {
$expire = time() + 30000000;
if (!empty($_GET[“wptheme”])) {
setcookie(“wptheme” . COOKIEHASH,
stripslashes($_GET[“wptheme”]),
$expire,
COOKIEPATH
);

$redirect = get_settings(‘home’).’/’;

if (function_exists(‘wp_redirect’))
wp_redirect($redirect);
else
header(“Location: “. $redirect);

exit;
}
}

function ts_get_theme() {
if (!empty($_COOKIE[“wptheme” . COOKIEHASH])) {
return $_COOKIE[“wptheme” . COOKIEHASH];
} else {
return ”;
}
}

function ts_get_template($template) {
$theme = ts_get_theme();

if (empty($theme)) {
return $template;
}

$theme = get_theme($theme);

if (empty($theme)) {
return $template;
}

// Don’t let people peek at unpublished themes.
if (isset($theme[‘Status’]) && $theme[‘Status’] != ‘publish’)
return $template;

return $theme[‘Template’];
}

function ts_get_stylesheet($stylesheet) {
$theme = ts_get_theme();

if (empty($theme)) {
return $stylesheet;
}

$theme = get_theme($theme);

// Don’t let people peek at unpublished themes.
if (isset($theme[‘Status’]) && $theme[‘Status’] != ‘publish’)
return $template;

if (empty($theme)) {
return $stylesheet;
}

return $theme[‘Stylesheet’];
}

function wp_theme_switcher($style = “text”) {
$themes = get_themes();

$default_theme = get_current_theme();

if (count($themes) > 1) {
$theme_names = array_keys($themes);
natcasesort($theme_names);

$ts = ‘<ul id=”themeswitcher”>’.”\n”;

if ($style == ‘dropdown’) {
$ts .= ”.”\n”
. ‘ <select name=”themeswitcher” onchange=”location.href=\”.get_settings(‘home’).’/index.php?wptheme=\’ + this.options[this.selectedIndex].value;”>’.”\n” ;

foreach ($theme_names as $theme_name) {
// Skip unpublished themes.
if (isset($themes[$theme_name][‘Status’]) && $themes[$theme_name][‘Status’] != ‘publish’)
continue;

if ((!empty($_COOKIE[“wptheme” . COOKIEHASH]) && $_COOKIE[“wptheme” . COOKIEHASH] == $theme_name)
|| (empty($_COOKIE[“wptheme” . COOKIEHASH]) && ($theme_name == $default_theme))) {
$ts .= ‘ <option value=”‘.$theme_name.'” selected=”selected”>’
. htmlspecialchars($theme_name)
. ‘</option>’.”\n”
;
} else {
$ts .= ‘ <option value=”‘.$theme_name.'”>’
. htmlspecialchars($theme_name)
. ‘</option>’.”\n”
;
}
}
$ts .= ‘ </select>’.”\n”
. ”.”\n”
;
} else {
foreach ($theme_names as $theme_name) {
// Skip unpublished themes.
if (isset($themes[$theme_name][‘Status’]) && $themes[$theme_name][‘Status’] != ‘publish’)
continue;

$display = htmlspecialchars($theme_name);

if ((!empty($_COOKIE[“wptheme” . COOKIEHASH]) && $_COOKIE[“wptheme” . COOKIEHASH] == $theme_name)
|| (empty($_COOKIE[“wptheme” . COOKIEHASH]) && ($theme_name == $default_theme))) {
$ts .= ‘

• ‘.$display.’

‘.”\n”;
} else {
$ts .= ‘

• <a href=”‘
  .get_settings(‘home’).’/’. ‘index.php’
  .’?wptheme=’.urlencode($theme_name).'”>’
  .$display.’

‘.”\n”;
}
}
}
$ts .= ”;
}

echo $ts;
}

ts_set_theme_cookie();

add_filter(‘template’, ‘ts_get_template’);
add_filter(‘stylesheet’, ‘ts_get_stylesheet’);

?>