Can't save xml file content in mysql with fopen/fwrite/fclose (php)

I think the issue was by ths following , According to this article, the fwrite() is a smidgen faster. (Link to Wayback Machine, because site no longer exists.)
My guess is that file_put_contents() is just a wrapper around those three methods anyways, so you would lose the overhead.

hope this fix your issue Did you wait long enough (don't know how long on android, more than 3 minutes at least) before removing the battery?
Android writes files to the flash only once every x seconds. If you want to make sure, your data is actually written to the flash, use the 'fsync' command.

I wish this helpful for you There is no need to set header while saving the target file on the server, but, if you want to be able to access that file (cross-domain) then you need to set Access-Control-Allow-Origin (exactly when you request that file from server).
In Your case: you saved json file {$this->name}.json on your sever, if you want to receive that file and set (Access-Control-Allow-Origin) then you need to read that file using PHP and then set header for example:

jsonnreador.php
<?php
header('Content-Type: application/json');
header('Access-Control-Allow-Origin: *');
echo file_get_contents('myjson.json');
?>

this will help In such cases, it might be even better to revert to open/write/close and get rid of C buffered output completely. Log files are typically consisting of a high volume of nearly identical (size-wise) writes and do not really gain much from C buffering. Low level, unbuffered I/O would also relieve you of calling fflush() and can guarantee to write every single log entry as atomic entity.
Given the volume you mentioned, you should probably still not close and re-open the file between writes.

Hope that helps fopen, fwrite, fclose don't throw Exceptions, they return errors
Try

try {
        // Open temp file for writing
        $tempFile = fopen("/var/www/dropbox/temp.lst", "w");
        if (false === $tempFile) throw new \RuntimeException("Failed to open file");

        echo "tempfile=" . $tempFile .  "<br>";

        // Write list of file names to file
        for ($x = 0; $x <= $inputFileCount; $x++) {
                if(false === fwrite($tempFile, $fileNames)) throw new \RuntimeException("Failed to write to file"); 
        }

        // Close temp file
        if(false === fclose($tempFile)) throw new \RuntimeException("Failed to close file"); 
} catch ( Exception $e ) {
        // send error message if you can
        echo 'Caught exception: ',  $e->getMessage(), "\n";
}