arrays - PHP memory exhaused while using array_combine in foreach loop

I'm having a trouble when tried to use array_combine in a foreach loop. It will end up with an error:

PHP Fatal error:  Allowed memory size of 268435456 bytes exhausted (tried to allocate 85 bytes) in

Here is my code:

$data = array();
$csvData = $this->getData($file);
if ($columnNames) {
    $columns = array_shift($csvData);
    foreach ($csvData as $keyIndex => $rowData) {
        $data[$keyIndex] = array_combine($columns, array_values($rowData));
    }
}
return $data;

The source file CSV which I've used has approx ~1,000,000 rows. This row

$csvData = $this->getData($file)

I was using a while loop to read CSV and assign it into an array, it's working without any problem. The trouble come from array_combine and foreach loop.

Do you have any idea to resolve this or simply have a better solution?

Here is the code to read the CSV file (using while loop)

$data = array();
if (!file_exists($file)) {
    throw new Exception('File "' . $file . '" do not exists');
}
$fh = fopen($file, 'r');
while ($rowData = fgetcsv($fh, $this->_lineLength, $this->_delimiter, $this->_enclosure)) {
    $data[] = $rowData;
}
fclose($fh);
return $data;

The code above is working without any problem if you are playing around with a CSV file <=20,000~30,000 rows. From 50,000 rows and up, the memory will be exhausted.