Create PDF Report

Tue Sep 18, 2018 by Bill Farmer. Categories: Hacking .

Introduction

As part of the Questionnaire Maker plugin it is necessary to create a pdf report. The best tool to do this appears to be TCPDF, which appears to be part of at least some Linux distributions as php-tcpdf. It is not included in WordPress.

Implementation

As both the plugin and TCPDF are hosted on GitHub, the best way to implement the plugin, and TCPDF if it is not available on the web server, is to clone the repositories and use symbolic links to provide the plugin and the library in the right places. The same method could be used to implement WordPress.

user@server:~ $ git clone https://github.com/billthefarmer/questionnaire.git
user@server:~ $ cd /var/www/html/wordpress/wp-content/plugins/
user@server:/var/www/html/wordpress/wp-content/plugins $ ln -s ~/questionnaire/wordpress questionnaire_maker
user@server:/var/www/html/wordpress/wp-content/plugins $ cd ~
user@server:~ $ git clone https://github.com/tecnickcom/TCPDF.git tcpdf
user@server:~ $ cd questionnaire/wordpress
user@server:~/questionnaire/wordpress $ ln -s ~/tcpdf

The plugin includes code to load TCPDF if it is present and show a message if it isn’t. Using the path tcpdf/tcpdf.php will pick it up either from /usr/share/php, if installed, or from the symbolic link.

// Include TCPDF, if present
$tcpdf_present = include_once 'tcpdf/tcpdf.php';

After more work on this project I needed another library which makes use of composer for dependencies. TCPDF doesn’t have any, but you can create a composer.json in the plugin and load TCPDF.

user@server:~/questionnaire/wordpress $ php composer.phar require tecnickcom/tcpdf

Using composer, the code to load libraries changes to pick them up from the vendor folder.

// Include composer libraries, if present
$vendor_present = include_once 'vendor/autoload.php'

Displaying errors

To avoid the dreaded WordPress White Screen of Death (WSOD), you can temporarily put a couple of lines at the top of the plugin to display PHP errors.

error_reporting(E_ALL);
ini_set('display_errors', 1);

Creating the document

The code to create a pdf document is fairly straightforward. The examples given always seem to specify everything, but by making note of the defaults, that isn’t necessary.

        // Create document
        $pdf = new TCPDF();
        $pdf->setPageUnit('pt');

        // Remove default header/footer
        $pdf->setPrintHeader(false);
        $pdf->setPrintFooter(false);

        $margin = 72; // 1"
        $pageWidth = $pdf->getPageWidth();
        $pageHeight = $pdf->getPageHeight();
        $textWidth = $pageWidth - ($margin * 2);

        // Set margins
        $pdf->SetMargins($margin, $margin, $margin);
        $pdf->SetAutoPageBreak(true, $margin);

TCPDF doesn’t seem to include a function to move the insertion point down a line, you need to nest three functions to get the right result. The functions to add text make use of the MultiCell() function. Also the SetFont() function is used to set the font type.

        // New line
        function new_text_line($pdf)
        {
            $pdf->Ln($pdf->getCellHeight($pdf->getFontSize()));
        };

        // Add text
        function add_text_object($pdf, $text, $forename = '', $lastname = '')
        {
            if (!empty($text->type))
                $pdf->SetFont('', $text->type);

            else
                $pdf->SetFont('', '');

            if (!empty($text->size))
                $pdf->SetFontSize($text->size);

            if (!empty($text->color))
                $pdf->SetTextColor($text->color);

            if (!empty($text->y))
                $pdf->SetY($text->y);

            $subst = str_replace(['~forename~', '~lastname~'],
                                      [$forename, $lastname], $text->text);

            $pdf->MultiCell(0, 0, $subst, 0, 'L');
        };

        // Add report entry
        function add_entry($pdf, $entry, $value)
        {
            $desc = $entry->desc;
            $type = $entry->$value->type;
            $text = $entry->$value->text;
            $image = $entry->$value->image;

            $y = $pdf->GetY();
            $pdf->Image($path . $image, $margin, $y, $textWidth, 0,
                        'png', '', 'N');

            $pdf->MultiCell(0, 0, $desc, 0, 'L');
            new_text_line($pdf);
            $pdf->SetFont('', 'B');
            $pdf->MultiCell(0, 0, $type, 0, 'L');
            new_text_line($pdf);
            $pdf->SetFont('', '');
            $pdf->MultiCell(0, 0, $text, 0, 'L');
            new_text_line($pdf);
        };

To display images requires a set of rules to place the image on the page. If the width is empty or zero, text width, else width. If the height is empty or zero, height in proportion to width, else height. If x is empty or zero, left margin, if negative, right margin, else x. If y is empty or zero, top margin, negative, bottom margin, else y.

        // Add image
        function add_image_object($pdf, $image, $margin, $textWidth,
                                  $pageHeight, $pageWidth, $path)
        {
            $width = (!empty($image->width))? $image->width: $textWidth;
            $height = (!empty($image->height))? $image->height: 0;
            $x = (!empty($image->x))? ($image->x < 0)?
               $pageWidth - $margin - $width: $image->x: $margin;
            $y = (!empty($image->y))? ($image->y < 0)?
               $pageHeight - $margin - $height: $image->y: $margin;
            $type = (!empty($image->type))? $image->type: '';
            $link = (!empty($image->link))? $image->link: '';
            $pdf->Image($path . $image->src, $x, $y, $width, $height,
                        $type, $link);
        };

The report starts with a preamble.


        // Preamble
        foreach ($pages as $page)
        {            
            $pdf->AddPage();

            // Text
            foreach ($page->text as $text)
                add_text_object($pdf, $text, $forename, $lastname);

            // Images
            foreach ($page->images as $image)
                add_image_object($pdf, $image, $margin, $textWidth,
                                 $pageHeight, $pageWidth, $path);
        }

Then the report body. Because each section starts with an image, start a new page if near the bottom.


        // Report
        $pdf->AddPage();

        if ($B)
            add_entry($pdf, $answers->B, $B, $margin, $textWidth, $path);

        if ($C)
            add_entry($pdf, $answers->C, $C, $margin, $textWidth, $path);

        if ($pdf->GetY() >= $pageHeight - ($margin * 3))
            $pdf->AddPage();
    // ...

Then the last page.


        $pdf->AddPage();

        // Last page text
        foreach ($last->text as $text)
            add_text_object($pdf, $text);

        // Last page images
        foreach ($last->images as $image)
            add_image_object($pdf, $image, $margin, $textWidth,
                             $pageHeight, $pageWidth, $path);

Output the document, and return the path to it.


        // Output document
        $pdf->Output($path . 'report/' . $filename, 'F');

        // Return file uri
        return plugins_url('report/' . $filename, __FILE__);

Creating an email

To send the report, create an email and send it.

        // Set fields
        $to = "$username <$usermail>";
        $from_email = $data->from_email;
        $from_name = $data->from_name;
        $from = "$from_name <$from_email>";
        $subject = str_replace('~forename~', $forename, $data->subject);
        $message = str_replace('~forename~', $forename, $data->message);
        $content = "Content-Type: text/html";
        $headers = ["From: $from",
                    $content];

        // Get attachment path
        $path = plugin_dir_path(__FILE__);
        $attachments = $path . "report/" . $filename;

        // Send mail
        wp_mail($to, $subject, $message, $headers,
                $attachments);

Bill Farmer