如何将具有相同ID的多行中的值连接到以唯一ID分隔的逗号

Question

I have a CSV file, name it data.csv , that looks like this:

id,position,data
1,1,Data text
1,2,Data text 2
1,3,Data text 3
2,1,Data text x
2,2,Data text y

What I need is to concatenate the values in the field data in a single one for all the rows with the same id . Then, print those newly obtained rows in another CSV file.

I managed to arrange the values in an array, but at the conversion to the CSV file it saves only one of them.

Here is my code

$file = 'data.csv';
$tsvFile = new SplFileObject($file);
$tsvFile->setFlags(SplFileObject::READ_CSV);
$tsvFile->setCsvControl(",");

foreach ($tsvFile as $line => $row) {
    if ($line > 0) {
            $newData[$row[0]] = array('id'=>$row[0], 'position'=>$row[1], 'data'=>$row[2]);
            $newData[$row[1]] = $row[2];
    }
}
//
echo '<pre>';
var_dump($newData);
//
$fp = fopen('data2.csv', 'w');
foreach ($newData as $fields) {
    fputcsv($fp, $fields);
}
fclose($fp);

At the end, the resulting CSV file should look like this:

id,data
"1","Data text, Data text 1, Data text 2"
"2","Data text x, Data text y"

Answer 1

Well, I think you could do what you ask in an easier way.

I just used fgetcsv() and fputcsv() functions to handle the extraction and insertion of a well formed and well formatted row from/to file.

$output = array();

if ($in_handle = fopen('data.csv', 'r')) {
    // discard the first line, the one with the names of the fields
    $input = fgetcsv($in_handle);

    // get an array out of a row from the file data.csv
    while ($input = fgetcsv($in_handle)) {
        // create an array with only the needed fields
        $current_row = array(
            'id' => $input[0],
            'data' => $input[2]
        );

        if (array_key_exists($current_row['id'], $output)) {
            $output[$current_row['id']]['data'] .= ' ' . $current_row['data'];
        } else {
            $output[$current_row['id']] = $current_row;
        }
    }

    fclose($in_handle);

    if ($out_handle = fopen('new_file.csv', 'w')) {
        // recreate the first line of the file deleted before
        $fields_names = array('id', 'data');
        fputcsv($out_handle, $fields_names);

        // begins at 1 because there isn't any value before
        for ($i = 1; $i <= count($output); ++$i)
            fputcsv($out_handle, $output[$i]);
    }

    fclose($out_handle);
}

Here's the input I used to test the script:

id,position,data
1,1,first string
1,2,second string
1,3,third string
2,1,fourth string
2,2,fifth string

And here's the output file i obtained:

id,data
1,"first string second string third string"
2,"fourth string fifth string"

As you can see, the data part of the rows is now quoted. That's just the way standard CSV handles strings.