How to assign SplFileObject::fpassthru output to variable

I'm currently writing some data to an SplFileObject like this:

$fileObj = new SplFileObject('php://text/plain,', "w+");

foreach($data as $row) {

    $fileObj->fputcsv($row);
}

Now, I want to dump the whole output (string) to a variable.

I know that SplFileObject::fgets gets the output line by line (which requires a loop) but I want to get it in one go, ideally something like this:

$fileObj->rewind();
$output = $fileObj->fpassthru();

However, this does not work as it simply prints to standard output.

There's a solution for what I'm trying to achieve using stream_get_contents():

pass fpassthru contents to variable

However, that method requires you to have direct access to the file handle.

SplFileObject hides the file handle in a private property and therefore not accessible.

Is there anything else I can try?

Solution

After writing, do a rewind() then you can read everything. The example is for understanding:

$fileObj = new SplFileObject('php://memory', "w+");
    
$row = [1,2,'test'];  //Test Data
    
$fileObj->fputcsv($row);
$fileObj->rewind();
    
//now Read
$rowCopy = $fileObj->fgetcsv();
    
var_dump($row == $rowCopy);//bool(true)

$fileObj->rewind();
$strLine = $fileObj->fgets();  //read as string
$expected = "1,2,test\n";

var_dump($strLine === $expected);  //bool(true)

//several lines
$fileObj->rewind();
$fileObj->fputcsv(['test2',3,4]);
$fileObj->fputcsv(['test3',5,6]);

$fileObj->rewind();
for($content = ""; $row = $fileObj->fgets(); $content .= $row);

var_dump($content === "test2,3,4\ntest3,5,6\n");  //bool(true)

If you absolutely have to fetch your content with only one command then you can do this too

// :
$length = $fileObj->ftell(); 
$fileObj->rewind();
$content = $fileObj->fread($length);

getSize() doesn't work here.