试图理解TCPDF

Question

我试图从PHP获得一个PDF文档。到目前为止一切都很好，但现在我正在努力：

while($row = mysqli_fetch_array($result))
  {
  $nombre_plato ="";
  $nombre_plato .=  "  ".recuperar_nombre_plato($row['plato_pedido'])."";

  $pdf->writeHTML($nombre_plato, true, 0, true, 0);
}

recuperar_nombre_plato($variable)是从另一个文件调用的函数。

如果我写：

$nombre_plato .=  "  ".$row['plato_pedido']."";

然后，输出与预期的相同($row‘’plato_pedido‘=1)，有4行：

​

​

但是使用所需的代码

$nombre_plato .=  "  ".recuperar_nombre_plato($row['plato_pedido'])."";

输出是空白，没有输出。该函数在其他files.The输出字符串上运行良好，显示在其他文件上，但这里不显示。

欢迎任何帮助..。

编辑：

function recuperar_nombre_plato ($recibido) {

/*** mysql hostname ***/
$hostname = 'XXX';

/*** mysql username ***/
$username = 'XXX';

/*** mysql password ***/
$password = 'XXX';

try {
    $dbh = new PDO("mysql:host=$hostname;dbname=XXX", $username, $password);
    /*** echo a message saying we have connected ***/



    $sql = "SELECT * FROM tb_platos WHERE id_plato = '".$recibido."'";
    foreach ($dbh->query($sql) as $row)
        {
        return $row['nombre_plato'];
        }


    $dbh = null;
}
catch(PDOException $e)
    {
    echo $e->getMessage();
    }


}

完整的源代码：

<?php session_start();
include "funciones.php"; 
include "definiciones.php";
require_once('tcpdf/config/lang/eng.php');
require_once('tcpdf/tcpdf.php');
// create new PDF document
$pdf = new TCPDF(PDF_PAGE_ORIENTATION, PDF_UNIT, PDF_PAGE_FORMAT, true, 'UTF-8', false);
// set document information
$pdf->SetCreator(PDF_CREATOR);
$pdf->SetAuthor('Dario Balas');
$pdf->SetTitle('PDF');
$pdf->SetSubject('PDF');
$pdf->SetKeywords('PDF');
// set default monospaced font
$pdf->SetDefaultMonospacedFont(PDF_FONT_MONOSPACED);
//set margins
$pdf->SetMargins(PDF_MARGIN_LEFT, PDF_MARGIN_TOP, PDF_MARGIN_RIGHT);
//set auto page breaks
$pdf->SetAutoPageBreak(TRUE, PDF_MARGIN_BOTTOM);
//set image scale factor
$pdf->setImageScale(PDF_IMAGE_SCALE_RATIO);
//set some language-dependent strings
$pdf->setLanguageArray($l);
// ---------------------------------------------------------
// set default font subsetting mode
$pdf->setFontSubsetting(true);
// Set font
// dejavusans is a UTF-8 Unicode font, if you only need to
// print standard ASCII chars, you can use core fonts like
// helvetica or times to reduce file size.
$pdf->SetFont('helvetica', 'B', 12);
// Add a page
// This method has several options, check the source code documentation for more information.
$pdf->AddPage();
// Set some content to print

$pdf->Image('imagenes/logo_restaurante.gif',20, 20, 20, 25, '', '', 'T', false, 72, '', false, false, 1, false, false, false);

$pdf->SetXY(20, 42);
$pdf->writeHTML($nombre_restaurante,'<br>');
$pdf->SetXY(20, 47);
$pdf->writeHTML($direccion_restaurante,'<br>');
$pdf->SetXY(20, 52);
$pdf->writeHTML($ciudad_restaurante,'<br>');
$pdf->SetXY(130, 12);
$pdf->writeHTML("Orden ".$_SESSION['pedido'],'<br>');
$pdf->SetFont('helvetica', 'B', 12);
$pdf->SetXY(130, 17);
$pdf->writeHTML("Fecha/Hora inicio: ",'<br>');
$pdf->SetFont('helvetica', '', 12);
$pdf->SetXY(130, 22);
$pdf->writeHTML(recuperar_fecha_pedido($_SESSION['pedido']),'<br>');
$pdf->SetFont('helvetica', 'B', 12);
$pdf->SetXY(130, 27);
$pdf->writeHTML("Le atendió: ",'<br>');
$pdf->SetXY(130, 32);
$pdf->SetFont('helvetica', '', 12);
$pdf->writeHTML(recuperar_nombre_usuario(recuperar_atendio_pedido($_SESSION['pedido'])),'<br>');
$pdf->SetFont('helvetica', 'B', 12);
$pdf->SetXY(130, 37);
$pdf->writeHTML("Mesa: ",'<br>');
$pdf->SetFont('helvetica', '', 12);
$pdf->SetXY(130, 42);
$pdf->writeHTML(recuperar_nombre_mesa(recuperar_mesa_pedido($_SESSION['pedido'])),'<br>');
$con=mysqli_connect("localhost","XXX","XXX","XXX");
// Check connection
if (mysqli_connect_errno())
  {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
  }
  $pdf->SetXY(15, 72);
  $x= 72;
  $nombre_plato ="";
$result = mysqli_query($con,"SELECT * FROM tb_lineas_comanda WHERE id_pedido = '".$_SESSION['pedido']."'");
while($row = mysqli_fetch_array($result))
  {

  $nombre_plato .=  "  ".recuperar_nombre_plato($row['plato_pedido'])."";


}

$pdf->writeHTML($nombre_plato, true, 0, true, 0);
// ---------------------------------------------------------
// Close and output PDF document
// This method has several options, check the source code documentation for more information.
$pdf->Output('', 'I');
//============================================================+
// END OF FILE
//============================================================+

?>

Answer 1

不能从函数返回多个东西，因此循环中的返回语句没有任何意义。因此，在这个循环中构建一个临时字符串，然后返回该字符串。

function recuperar_nombre_plato ($recibido) {
    $hostname = 'XXX';
    $username = 'XXX';
    $password = 'XXX';

    try {
        $dbh = new PDO("mysql:host=$hostname;dbname=XXX", $username, $password);
        $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

        $sql = "SELECT * FROM tb_platos WHERE id_plato = '".$recibido."'";
        $str = '';
        foreach ($dbh->query($sql) as $row) {
            $str .= $row['nombre_plato'];
        }
        return $str;

        // nothing happens after a return so this will never get run
        //$dbh = null;  
    }
    catch(PDOException $e) {
        echo $e->getMessage();
    }
}

或者，如果由于id_plato是唯一的键，查询只能返回一行，则更改代码以反映这一事实。

function recuperar_nombre_plato ($recibido) {
    $hostname = 'XXX';
    $username = 'XXX';
    $password = 'XXX';

    try {

        $dbh = new PDO("mysql:host=$hostname;dbname=XXX", $username, $password);
        $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

        $sql = "SELECT * FROM tb_platos WHERE id_plato = '".$recibido."'";

        $stmt = $dbh->query($sql);
        $row = $stmt->fetch(PDO::FETCH_ASSOC);
        return $row['nombre_plato'];

        // nothing happens after a return so this will never get run
        //$dbh = null;  
    }
    catch(PDOException $e) {
        echo $e->getMessage();
    }
}

此外，在您的主函数中，当您从多个对recuperar_nombre_plato()的调用构建文本字符串时，您不希望将调用移到循环之外的$pdf->writeHTML。循环之前的$nombre_plato初始化如下:-

$nombre_plato ="";
while($row = mysqli_fetch_array($result)) {
   $nombre_plato .= "  ".recuperar_nombre_plato($row['plato_pedido']);
}
$pdf->writeHTML($nombre_plato, true, 0, true, 0);