PHP - create CSV file from POST $data = curl_exec($ch); that Contains only 1 big String

I did $data = curl_exec($ch); with POST method.
When I did echo '<pre>',var_dump($data),'</pre>';

string(15124) ""A","B","C","D","E","F","G","H"
,"2",,"4","5",,,"8"
"ONE",,,"QW AH",,"US",,"EU""

I tried to split them and make into array $lines = str_getcsv($data, PHP_EOL);
But I got only 1 array with everything in it
echo '<pre>',var_dump($lines),'</pre>';

array(1) {
  [0]=>
  string(15121) ""A","B","C","D","E","F","G","H"
,"2",,"4","5",,,"8"
"ONE",,,"QW AH",,"US",,"EU""

I want to create a csv file from that. So I did

$fp = fopen('../myfile.csv','w');
    fputcsv($fp, $data);
fclose($fp);

I got the file, but when opened in excel the columns are not right.
How to actually split them row by row?
Thanks.

Note that your data are already a csv. In short you have nothing to do except to save it to a file with file_put_contents.

About your approach:
You obtain only one item in your array because:

• str_getcsv is designed to read only one line of csv, not a whole csv string with multiple lines.
• the second parameter of str_getcsv is not the line separator (see the manual) but the item separator that isn't a newline.

But if you want to change how the csv looks like (the delimiter, the protection or escape character, the newline sequence), you have to read it and to write it line by line. A simple way to do that is to use fopen() with the data:// wrapper, for example, to obtain a resource from a simple string. This way you don't have to split your data by lines since fgetcsv does it for you:

$data = '"A","B","C","D","E","F","G","H"
,"2",,"4","5",,,"8"
"ONE",,,"QW AH",,"US",,"EU"';
    
$fhi = fopen('data://text/plain;base64,' . base64_encode($data), 'r');

if (false !== $fho = fopen('output.csv', 'w')) {
    while (false !== $row = fgetcsv($fhi)) {
        fputcsv($fho, $row, ';', '"', '\\', "\n"); // choose the parameters
    }
    
    close($fho);
}

close($fhi);

It seems some Microsof Excel versions tend to use semicolon ';' instead of comma ',' as seen at (https://answers.microsoft.com/en-us/msoffice/forum/all/excel-keeps-on-using-semicolon-instead-of-comma/543510d9-65a8-4a0d-8464-a08fc0ac1c4f). It also may depend on locale and user settings.

In such case, changes from ',' to ';' may be needed according to user request.

E.g., for the data below...

// obtained data
$data = '"A","B","C","D","E","F","G","H"
,"2",,"4","5",,,"8"
"ONE",,,"QW AH",,"US",,"EU"';

// break it into lines
$lines = explode(PHP_EOL, $data);

// haven for the formatted rows
$csv_rows = [];

foreach ($lines as $line) {
	// Breaks each line into cells by the comma,
	// ignoring eventual commas inside values
	$cells = preg_split('/,(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)/', $line);

	// joins cells with semicolon
	$csv_rows[] = implode(';', $cells);
}

// result
$csv_text = implode(PHP_EOL, $csv_rows);

Result text:

"A";"B";"C";"D";"E";"F";"G";"H"
;"2";;"4";"5";;;"8" "ONE";;;"QW
AH";;"US";;"EU"

Tested within PHP Sandbox
→ https://onlinephp.io/c/23cc3

Improvements are welcome.

Just for my own reminder or anyone interested. This is what I do to finally get the file that I wanted.
Remove

$fp = fopen('../myfile.csv','w');
    fputcsv($fp, $data);
fclose($fp);

and change to file_put_contents('../myfile.csv','w');

Thank you very much guys for explaining me that and showing even more bonus knowledge