Multiple users write to the same file at the same time using PHP

Question

I have a website where at the same moment, there can be multiple users writing to the same file at the same time. An example of my code is below.

PHP 5.6

Answer 1

If two scripts attempt to write to a file at the same time. The fopen() function, when called on a file, does not stop that same file from being opened by another script, which means you might find one script reading from a file as another is writing, or, worse, two scripts writing to the same file simultaneously. So it is good to use flock() . You can get more help on http://www.hackingwithphp.com/8/11/0/locking-files-with-flock . For your code you may use flock() as

";
$filename=$root."/Testing/Testing/test1.txt";

$myfile=fopen($filename,"a");
if (flock($myfile, LOCK_EX)) {        
    fwrite($myfile,$var);
    flock($myfile, LOCK_UN); // unlock the file
} else {
    // flock() returned false, no lock obtained
    print "Could not lock $filename!\n";
}

fclose($myfile);

$myfile=fopen($filename,"r");
if (flock($myfile, LOCK_EX)) {        

    $contents = fread($myfile, filesize($filename));
    echo $contents;
    flock($myfile, LOCK_UN); // unlock the file
} else {
    // flock() returned false, no lock obtained
    print "Could not lock $filename!\n";
}
fclose($myfile);
?>