PDFLib工厂。从类中的函数调用$ this-> pdf时出错

Question

这个想法如下，为了使PDF的创建更加清晰，我应该创建一个Factory / Abstract类，它将具有一组预定义的函数，如此

class AbstractPDF{

    protected $pdf;
    protected $searchpath;

    public function __construct(){

        $this->pdf = PDF_new();
        $this->searchpath = "fonts/";

        pdf_set_option($this->pdf,"errorpolicy=return");

        pdf_set_option($this->pdf,"searchpath={" . $this->searchpath . "}");

        pdf_set_option($this->pdf,"stringformat=utf8");

    }

    protected function startAFourPage(){

        pdf_begin_page_ext($this->pdf, 0, 0, "width=a4.width height=a4.height");
                }



    /* When setting up any of the PDF content types, one should */
    /* remember that in PDFLib, x=>y axis start with 0(zero) at */
    /* lower left corner.                                       */
    /* The text line is set up in space by setting up the       */
    /* coordinates of the lower left corner and then providing  */
    /* height and width of the object as separate values        */  



protected function setupTextLine($xcoordinate, $ycoordinate, $width, $height,
                        $fontName, $fontEncoding, $fontSize, $text, $textPosition = "left"){

        //adding text directly through the PDFLib documentation
        $font = PDF_load_font($this->pdf, $fontName, $fontEncoding, "");
        PDF_setfont($this->pdf, $font, $fontSize);
        //PDF_set_text_pos($this->pdf, 25, 650);
        //PDF_show($this->pdf, $text);
        PDF_fit_textline ($this->pdf, $text, 111, 744, "boxsize {".$width." ".$height."} position=left");

    }


    /* When setting up any of the PDF content types, one should */
    /* remember that in PDFLib, x=>y axis start with 0(zero) at */
    /* lower left corner.                                       */
    /* The text flow is set up by providing the coordinate for  */
    /* lower left corner and upper right, as a rule.            */
    /* But overall PDFLib will placed it by coordinates for     */
    /* two corners diagonal to each other.                      */
    /* For this class we will identify these corners as         */
    /* lowLeft and upperRight                                   */


protected function setupMultilineTextflow($lowLeftX, $lowLeftY, $upperRightX, $upperRightY,
                        $fontName, $fontEncoding, $fontSize, $text){

        $orderDetails = 'Datum:
        Auftrags-NR:
        Auftragsname:
        Kunden-Nr:';

        $textFlow = PDF_create_textflow($this->pdf, $text, 
                    "fontname=".$fontName." 
                    fontsize=".$fontSize." 
                    encoding=".$fontEncoding);
        PDF_fit_textflow($this->pdf, $textFlow3, $lowLeftX, $lowLeftY, $upperRightX, $upperRightY,"");

    }

    protected function setupTable($headers=array('test'=>''), array $field){        
                }

}
?>

此类从以下调用

class PDF extends AbstractPDF{

    public function __construct(){

        parent::__construct();

        parent::startAFourPage();

    }

    public function generateContent(){

        return "";

    }


}

我为拥有这么多代码而道歉，但我想画一幅完整的图片。

问题是，当我尝试调用这些类时，我收到以下错误：

2017/12/19 18:47:58 [错误] 465＃465：* 252在stderr中发送FastCGI：“PHP消息：PHP致命错误：未捕获PDFlibException：函数不能在/ var / www中的'object'范围内调用/dev-vm-stretch.de/htdocs/AbstractPDF.php:30

堆栈跟踪：

＃0 /var/www/dev-vm-stretch.de/htdocs/AbstractPDF.php(30）：pdf_begin_page_ext（资源ID＃1,0,0，'width = a4.width ...'）

＃1 /var/www/dev-vm-stretch.de/htdocs/PDF.php(10）：AbstractPDF-> startAFourPage（）

＃2 /var/www/dev-vm-stretch.de/htdocs/index.php(18）：PDF - > __ construct（）

＃3 {main}

在第30行的/var/www/dev-vm-stretch.de/htdocs/AbstractPDF.php中抛出“从上游读取响应头，客户端：192.168.34.51，服务器：dev-vm-stretch.de，请求：” GET /index.php HTTP / 1.1“，上游：”fastcgi：// unix：/var/run/php/php7.0-fpm.sock：“，主持人：”dev-vm-stretch.de“

我认为这是因为我将PDFLib相关代码分离为函数，但我并不是百分之百确定，因为我的PDFLib经验仅限于5天以上，而且我还没有找到任何可以解决这些问题的PDFLib教程:-(

关于如何解决这个错误的任何想法都受到欢迎。

Answer 1

问题很简单。只有输出文档时，才能创建页面。您可以使用begin_document($file, $options);创建一个新的输出文档。您也可以使用__construct。

您可以查看PDFlib 9.1.1 API参考，第1.2章“函数范围”。此外，所有PDFlib PHP示例（包括PDFlib PHP包中）都演示了正确的用法。