1. Navigate to the WordPress plugin directory of your development installation.
2. Navigate to the ch8-bug-tracker directory and edit ch8-bug-tracker.php.
3. Find the ch8bt_shortcode_list function and add the following highlighted code after the initial global $wpdb call to check whether a search string was entered by a visitor:

global $wpdb; 
 
if ( !empty( $_GET['searchbt'] ) ) { 
    $search_string = sanitize_text_field( $_GET['searchbt'] ); 
    $search_mode = true; 
} else { 
    $search_string = "Search..."; 
    $search_mode = false; 
} 

4. Insert the following highlighted lines of code in the middle of the existing query string to add the where parameters using the user search text, if present:

$bug_query = 'select * from ' . $wpdb->get_blog_prefix(); 
$bug_query .= 'ch8_bug_data ';

// Add search string in query if present 
if ( $search_mode ) { 
    $search_term = '%'. $search_string . '%'; 
    $bug_query .= "where bug_title like '%s' "; 
    $bug_query .= "or bug_description like '%s' "; 
} else { 
    $search_term = ''; 
}

$bug_query .= 'ORDER by bug_id DESC'; 

5. Locate the following line of code:

$bug_items = $wpdb->get_results( $bug_query, ARRAY_A );

Replace it to the following code:

if ( $search_mode ) {
    $bug_items = $wpdb->get_results( $wpdb->prepare(  
                     $bug_query, $search_term, $search_term ), 
                     ARRAY_A );
} else {
    $bug_items = $wpdb->get_results( $bug_query, ARRAY_A );
}

6. Add the following code block, before the table starts rendering, to display a simple search form:

$output = '';

$output .= '<div class="ch8_bt_search">';
$output .= '<form method="get" id="ch8_bt_search">'; 
$output .= '<div>Search bugs '; 
$output .= '<input type="text" onfocus="this.value=\'\'" '; 
$output .= 'value="' . esc_html( $search_string ) . '" '; 
$output .= 'name="searchbt" />'; 
$output .= '<input type="submit" value="Search" />'; 
$output .= '</div>'; 
$output .= '</form></div>'; 
 
$output .= '<div class="bug-tracker-list"><table>'; 

7. Save and close the plugin file.
8. Visit the bug display page that was previously created to see the new search form. Enter a search string and click on the Search button to see a list of results: