Replace stuff in content

gistfile1.txt

<?php
if(is_user_logged_in()){
$args = array(
	'sort_order'  => 'asc',
	'sort_column' => 'post_title',
	'post_type'   => 'page',
    'numberposts' => -1,
	'post_status' => 'any',
    'suppress_filters' => true
); 
$pages = get_posts($args);
echo '<table>';
foreach($pages as $page){ //pre($page);
    $nr = $_GET['nr'];
    $string_to_look_for = "[$nr]";
    $replace_with       = '<a href="#viited"><sup>'.$nr.'</sup></a>';
    
    //$string_to_look_for = '<a href="#_ftn19" name="_ftnref19">[19]</a>';
    //$replace_with       = '<a href="#viited" name="_ftnref19">19</a>';
    
    //$string_to_look_for = '<sup><a href="#viited"><sup>1</sup></a></sup>';
    //$replace_with       = '<a href="#viited"><sup>1</sup></a>';
    $original_content = $page->post_content;
    $new_content = (substr_count($original_content, $string_to_look_for) > 0) ? str_replace($string_to_look_for, $replace_with, $original_content) : $original_content;
    $warning = (substr_count($original_content, $string_to_look_for) > 0) ? 'style="background:pink;"': '';
    
    if(substr_count($original_content, $string_to_look_for) > 0){
        echo '<tr '.$warning.'><td style="padding:10px;"><a href="'.str_replace('palm', 'kairi', get_permalink($page->ID)).'" target="_blank" style="color:#000;text-decoration:underline">'.$page->post_title.'</a></td><td style="padding:10px;">'.wp_trim_words(apply_filters('the_content', $original_content)).'</td><td style="padding:10px;">'.wp_trim_words(apply_filters('the_content', $new_content)).'</td></tr>';

        $my_post = array(
            'ID'           => $page->ID,
            'post_content' => $new_content
        );
        if(isset($_GET['update'])) wp_update_post($my_post);
    }
    
    /*
    $widgets = get_field('widgets', $page->ID);
    
    if($widgets && is_array($widgets)){ //pre($widgets);
        foreach($widgets as $widget){
            if($widget['acf_fc_layout'] == 'viited' ){
                //if(!empty($widget['viited_sisu'])){
                    //echo '<tr><td style="padding:10px;"><a href="'.str_replace('palm', 'kairi', get_permalink($page->ID)).'" target="_blank">'.$page->post_title.'</a></td><td>'.$widget['viited_sisu'].'</td></tr>';
                    
                //}
            }
        }
    } else {
        //echo '<tr style="background:pink;"><td style="padding:10px;"><a href="'.str_replace('palm', 'kairi', get_permalink($page->ID)).'" target="_blank">'.$page->post_title.'</a></td><td></td></tr>';
    }
    */
    
}
echo '</table>';
}
?>