PHP:将MYSQL查询写入CSV

Question

我正试图将MySQLi查询写入可下载的CSV。以下标题打开CSV的流：

$fileName = ''; //empty file name, file name is cast later
header("Cache=Control: must-revalidate, post-check=0, pre-check=0");
header('Content-Description: File Transfer');
header("Content-type: text/csv");
header("Content-Disposition: attachment; filename={$fileName}");
header("Expires: 0");
header("Pragma: public");
$fh = @fopen( 'php://output', 'w' );

下面我有以下内容，试图查询并将查询的每一行强制转换为CSV文件中的新行：

if(isset($_POST["Submit"]) && ($_POST['Weight'] == 'Weight')){
    $fileName .= 'OutputWeightNull.csv';
    $query = mysqli_query($conn, 'SELECT * FROM  `Some_Table` WHERE WEIGHT = 0 OR weight IS NULL')or die(mysql_error());
    $result = mysqli_fetch_array($query) or die(mysql_error());
    $headerDisplayed = false;
    foreach ($result as $data){
    if (!headerDisplayed){
    fputcsv($fh, array_keys());
    $headerDisplayed = true;
        }
        fputcsv($fh, $data);
    }
}

CSV正在根据需要下载到浏览器，但它显示为空，查询结果不会发送到CSV。有人能告诉我为什么会这样吗？

这是我第一次尝试使用比hello世界更复杂的PHP脚本。如果答案非常简单或明显，请道歉。

Answer 1

清理代码一次，以循环返回的行，并使用mysqli_error函数：-

<?php 
if(isset($_POST["Submit"]) && ($_POST['Weight'] == 'Weight'))
{
    $fileName = ''; //empty file name, file name is cast later
    header("Cache=Control: must-revalidate, post-check=0, pre-check=0");
    header('Content-Description: File Transfer');
    header("Content-type: text/csv");
    header("Content-Disposition: attachment; filename={$fileName}");
    header("Expires: 0");
    header("Pragma: public");
    $fh = @fopen( 'php://output', 'w' );
    $fileName .= 'OutputWeightNull.csv';
    $query = mysqli_query($conn, 'SELECT * FROM  `Some_Table` WHERE WEIGHT = 0 OR weight IS NULL') or die(mysqli_error($conn));
    if ($result = mysqli_fetch_array($query, MYSQLI_ASSOC))
    {
        fputcsv($fh, array_keys($result));
        fputcsv($fh, $result);
        while ($result = mysqli_fetch_array($query, MYSQLI_ASSOC))
        {
            fputcsv($fh, $result);
        }
    }
}

Answer 2

像这样尝试

if(isset($_POST["Submit"]) && ($_POST['Weight'] == 'Weight')){
 $fileName = 'OutputWeightNull.csv';
 $fh = @fopen( 'php://output', 'w' );
 header("Cache=Control: must-revalidate, post-check=0, pre-check=0");
 header('Content-Description: File Transfer');
 header("Content-type: text/csv");
 header("Content-Disposition: attachment; filename={$fileName}");
 header("Expires: 0");
 header("Pragma: public");
 $query = mysqli_query($conn, 'SELECT * FROM  `Some_Table` WHERE WEIGHT = 0 OR weight IS NULL')or die(mysql_error());
 $headerDisplayed = false;
 while($result = mysqli_fetch_array($query, MYSQLI_ASSOC)) {  
  if (!$headerDisplayed){
   fputcsv($fh, array_keys($result));
   $headerDisplayed = true;
  }
  fputcsv($fh, $result);
 }
}

您需要将csv标头放置在"if"循环

Answer 3

MySQL有一个内置的查询类型，用于将数据直接输出为CSV格式。

修改您的SELECT查询，使其具有以下格式：

SELECT fieldlist FROM table
INTO OUTFILE 'filename.csv'
FIELDS TERMINATED BY ','
ENCLOSED BY '"'
LINES TERMINATED BY 'n';

现在你不需要做任何循环或类似的事情；PHP所要做的就是运行该查询，然后对MySQL生成的CSV文件执行readfile()，最后将其从磁盘中删除。

这将为您的PHP程序节省大量内存，运行速度也会更快（如果您有一个大数据集，这将非常值得注意）。