我试图制作一个可以生成报告的PHP页面，但我一直收到此消息

Question

我试图制作一个可以生成报告的PHP页面，但是我一直收到此消息

  

警告：mysqli_fetch_array（）期望参数1为mysqli_result，在第8行的C：\ xampp \ htdocs \ Report.php中给出的布尔值我无法显示数据库中的内容

<?php  
 function fetch_data()  
 {  
      $output = '';  
      $conn = mysqli_connect("localhost", "root", "", "neo");  
      $sql = "SELECT * FROM product_order ORDER BY id ASC";  
      $result = mysqli_query($conn, $sql);
      while($row = mysqli_fetch_array($result))  
      {       
      $output .= '<tr>  
                          <td>'.$row["odID"].'</td>  
                          <td>'.$row["cusID"].'</td>  
                          <td>'.$row["total"].'</td>  
                          <td>'.$row["or_date"].'</td> 
                          <td>'.$row["or_qty"].'</td>
                          <td>'.$row["price"].'</td> 
                     </tr>  
                          ';  
      }  
      return $output;  
 }  
 if(isset($_POST["generate_pdf"]))  
 {  
      require_once('Tcpdf.php');  
      $obj_pdf = new TCPDF('P', PDF_UNIT, PDF_PAGE_FORMAT, true, 'UTF-8', false);  
      $obj_pdf->SetCreator(PDF_CREATOR);  
      $obj_pdf->SetTitle("Generate HTML Table Data To PDF From MySQL Database Using TCPDF In PHP");  
      $obj_pdf->SetHeaderData('', '', PDF_HEADER_TITLE, PDF_HEADER_STRING);  
      $obj_pdf->setHeaderFont(Array(PDF_FONT_NAME_MAIN, '', PDF_FONT_SIZE_MAIN));  
      $obj_pdf->setFooterFont(Array(PDF_FONT_NAME_DATA, '', PDF_FONT_SIZE_DATA));  
      $obj_pdf->SetDefaultMonospacedFont('helvetica');  
      $obj_pdf->SetFooterMargin(PDF_MARGIN_FOOTER);  
      $obj_pdf->SetMargins(PDF_MARGIN_LEFT, '10', PDF_MARGIN_RIGHT);  
      $obj_pdf->setPrintHeader(false);  
      $obj_pdf->setPrintFooter(false);  
      $obj_pdf->SetAutoPageBreak(TRUE, 10);  
      $obj_pdf->SetFont('helvetica', '', 11);  
      $obj_pdf->AddPage();  
      $content = '';  
      $content .= '  
      <h4 align="center">Order Report</h4><br /> 
      <table border="1" cellspacing="0" cellpadding="3">  
           <tr>  
                <th width="5%">Customer ID</th>  
                               <th width="30%">Order ID</th>  
                               <th width="15%">Total</th>  
                               <th width="50%">Order date</th>
                              <th width="75%">Order quantity</th>
                              <th width="100%">Price</th>  
           </tr>  
      ';  
      $content .= fetch_data();  
      $content .= '</table>';  
      $obj_pdf->writeHTML($content);  
      $obj_pdf->Output('file.pdf', 'I');  
 }  
 ?>