general/error_handling

<?php

/* $Id: error_handling.php,v 1.2 2012/05/03 14:00:39 stm Exp $

 * Error handling:

 * Demonstrate different strategies with respect to exception handling.

 *

 * Example 1: Set the "errorpolicy" parameter to "return". This means that a

 * PDFlib function call will return with -1 (in PHP: 0) when an error condition

 * is detected. Try to load a font which is not available so that load_font()

 * will return with -1 (in PHP: 0). Check for that return value and load another

 * available font instead.

 *

 * Example 2: Set the "errorpolicy" parameter to "exception". This means that

 * an exception will be thrown whenever a PDFlib function call fails. Change the

 * error policy to "return" every time you want to check the return value of a

 * particular PDFlib function call. Then, set the "errorpolicy" parameter to

 * "return" to check the return value of load_image(). If the image to be loaded

 * does not exist output a replacement text.

 *

 * Required software: PDFlib Lite/PDFlib/PDFlib+PDI/PPS 7

 * Required data: none

 */

/* This is where the data files are. Adjust as necessary. */

$searchpath = dirname(dirname(dirname(__FILE__)))."/input";

$outfile = "";

$title = "Error Handling";

$imagefile = "unavailable.jpg";

try {

    $p = new PDFlib();

    $p->set_parameter("SearchPath", $searchpath);

    $p->set_parameter("textformat", "utf8");

            

    /* Use the "errorpolicy" parameter to define an appropriate error

     * policy.

     * The default setting "errorpolicy=legacy" ensures compatibility to

     * earlier versions of PDFlib, where exceptions and error return values

     * are controlled by parameters and options such as fontwarning,

     * imagewarning, etc. This is only recommended for applications which

     * require source code compatibility with PDFlib 6.

     *

     * With "errorpolicy=exception" an exception will be thrown when an

     * error condition is detected. However, the output document will be

     * unusable after an exception. This can be used for lazy programming

     * without any error conditionals at the expense of sacrificing the

     * output document even for problems which may be fixable by the

     * application.

     *

     * With "errorpolicy=return" when an error condition is detected, the

     * respective function will return with a -1 (in PHP: 0) error value

     * regardless of any warning parameters or options. The application

     * developer must check the return value to identify problems, and must

     * react on the problem in whatever way is appropriate for the

     * application. This is the recommended approach since it allows a

     * unified approach to error handling.

     */

   

    /* ------------------------------------------------------------------

     * First example:

     * Set the "errorpolicy" to "return" for all function calls.

     * This means we must check the return values of load_font() etc. for

     * -1 (in PHP: 0).

     * ------------------------------------------------------------------

     */

    $p->set_parameter("errorpolicy", "return");

    if ($p->begin_document($outfile, "") == 0)

        throw new Exception("Error: " . $p->get_errmsg());

    $p->set_info("Creator", "PDFlib Cookbook");

    $p->set_info("Title", $title);

    /* Start page */

    $p->begin_page_ext(842, 595, "");

    /* Try to load a special font which might not be available.

     *

     * For PDFlib Lite: change "unicode" to "winansi"

     */

    $font = $p->load_font("MyFontName", "unicode", "");

    /* Check the return value of load_font() */

    if ($font == 0) {

        /* font handle is invalid; find out what happened */

        $errmsg = $p->get_errmsg();

       

        /* Try a different font */

        $font = $p->load_font("Helvetica", "unicode", "");

        /* font handle is also invalid; give up */

        if ($font == 0) {

            throw new Exception("Error: " . $p->get_errmsg());

        }

       

        /* Output the error message to the PDF. This is not pretty

         * realistic but it is intended to show how you can proceed after

         * a failed function call without having damaged the PDF.

         */

        $p->setfont($font, 20);

        $p->fit_textline($errmsg, 50, 400, "");

    }

   

    /* -------------------------------------------------------------------

     * Second example:

     * Set the "errorpolicy" to "exception". Change it to "return" only if

     * you want to check the return value of a particular function call.

     * -------------------------------------------------------------------

     */

    $p->set_parameter("errorpolicy", "exception");

   

    /* Output some descriptive text */

    $p->setfont($font, 20);

    $p->fit_textline("Error policy can be legal, exception, or return.",

        50, 500, "");

   

    /* Set the "errorpolicy" parameter  to "return" to check the return

     * value of load_image(). Then set the parameter back to "exception"

     * again. If the image to be loaded does not exist a replacement text

     * will be output.

     *

     * Alternatively, the "errorpolicy=return" option of load_image() can be

     * used which changes the error policy just for the respective function

     * call. Note that this option is correctly supported only by

     * PDFlib 7.0.3 and above.

     */

    $p->set_parameter("errorpolicy", "return");

     

    /* Load the image */

    $image = $p->load_image("auto", $imagefile, "");

   

    /* Set the "errorpolicy" parameter  to "exception" again */

    $p->set_parameter("errorpolicy", "exception");

   

    /* Output some replacement text if image is not available */

    if ($image == 0) {

        $p->setcolor("fillstroke", "rgb", 1, 0, 0, 0);

        $x=50; $y=200; $w=200; $h=100;

        $p->rect($x, $y, $w, $h);

        $p->stroke();

        $p->setfont($font, 10);

        $p->fit_textline("Replacement text for unavailable image",

            $x + 5, $y + 5, "boxsize={" . ($w - 10) . " " . ($h - 10) . "}");

    }

    else {

        /* Place the image */

        $p->fit_image($image, 20, 20, "scale=0.5");

    }

   

    $p->end_page_ext("");

    $p->end_document("");

    $buf = $p->get_buffer();

    $len = strlen($buf);

    header("Content-type: application/pdf");

    header("Content-Length: $len");

    header("Content-Disposition: inline; filename=error_handling.pdf");

    print $buf;

} catch (PDFlibException $e){

    die("PDFlib exception occurred:\n" .

        "[" . $e->get_errnum() . "] " . $e->get_apiname() .

        ": " . $e->get_errmsg() . "\n");

} catch (Exception $e) {

    die($e->getMessage());

}

$p=0;

?>