How do I use flock to read and write to files?

I tried to use flock but it just ends up deleting the contents of my file. I want flock() to let other application read, but not write to this file.

PHP code:

$filename = '../text/file.txt';
$fw = fopen($filename, "wrb");
$fl = flock($fw, LOCK_SH);
$data = 'hello';
$numbytes = fwrite($fw, $data);
flock($fw, LOCK_UN);

Code (markup):

Thanks.

And mabye someone could tell me how to change a PHP array into a Javascript array?

 

You are opening the file with "write and read" access....... write will open at position 0 and truncate the file, hence why its overwriting. If you need to append to the file then you should be looking to use a+

 

I'm confused. What do you mean by a+ I googled it and came up with nothing.
Would this work to append my data?

PHP code:

$filename = '../text/file.txt';
$fw = fopen($filename, "wrb");
$fl = flock($fw, LOCK_SH);
[COLOR="blue"]$data = fread($fw, filesize($filename))
$data .= ' hello';[/COLOR]
$numbytes = fwrite($fw, $data);
flock($fw, LOCK_UN);

Code (markup):

 

When you are opening the file here;

$fw = fopen($filename, "wrb");

PHP:

You are opening with mode "wrb" - by opening a file for Write, it will truncate the file to 0 bytes; that is, remove all the data. You should open with mode a+ and not mode wr if you want to add onto the end of it.

No - as the file will be truncated when opened (so it will be 0 bytes).

 

Thanks lukeg32. Using a+b worked!