Re: [PHP] file locks

[rarmin]

Liam Gibbs wrote:
 Is there a way for a script to tell if the file it's
 trying to access is locked by other script (via
 flock()) or not. I need to make script wait untill
 other script running in a parallel thread releases the
 lock on  the file.
 
 Without testing, would this work? Just a suggestion
 (read: shot in the dark) that may work.
 
 while(!$filehandle) {
$filehandle = fopen(file_in_question,
 r/w/whatever);
 }
 
 
 Tnx in advance.
 
 You're welcome in advance. :)
 
 
 __
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How is it possible that the file locked with exclusive lock can be 
opened by another call to fopen in the same script? Am i getting it all 
wrong, or the second call to fopen in the next code should fail?

$fp=fopen(somefile, w);
flock($fp, LOCK_EX);
$fp1=fopen(somefile, w);

I'm using php 4.1.2 windows version on apache 1.2.23.

Armin


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[PHP] file locks

[rarmin]

Is there a way for a script to tell if the file it's trying to access is 
locked by other script (via flock()) or not. I need to make script wait 
untill other script running in a parallel thread releases the lock on 
the file.

Tnx in advance.

Armin


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[PHP] sessions and passing variables

[rarmin]

Is there a way to pass variables (objects) across the different 
sessions. I thought of sharing one object for all users that access my 
web site (it's an object that does some operations with files common to 
all users, like reading and writing). Any ideas?

Tnx in advance.
Armin


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[PHP] Re: sessions and passing variables

[rarmin]

Michael Virnstein wrote:
 you also have to make sure, that only one user can access the file for
 writing at one time, or your data gets probably
 screwed. The easiest way would be storing the object not in a file but in a
 database, so you don't have to care about locking.

Tnx for the help, and one more question. If I would serialize object and 
store it in a file, I would need some way to implement object waiting at 
the locked file untill it's unlocked (some kind of semaphore or 
monitor). I can lock the file with flock, but I don't know how to put 
object on hold while the file it's requesting is locked. As for the 
database, I don't use database (it's an assignment that needs to be done 
using XML, so all data is in XML files) and I don't see much sence in 
using db for storing only one serialized object.

 
 But do you really need the same instance of the object? why not simply
 perform a $obj = new Class();

If I figure out how to put on hold object while some other object 
performs it's operations on locked file, I wouldn't need to use the same 
instance.

 
 
 --
 Code for Storing:
 ?php
 
 $strData = serialize($data);
 
 $fp = fopen(globalObjectData.inc, w);
 fwrite($fp, $strData);
 fclose($fp);
 
 ?
 
 Code for accessing:
 
 ?php
 
 // include object source before unserializing
 include myObjectSrc.php;
 
 $fp = fopen(globalObjectData.inc, w);
 $strData = fread($fp, filesize(globalObjectData.inc));
 fclose($fp);
 
 // so we have our object back
 $obj = unserialize($strData);
 
 
 

Does anyone know how to implement monitor or semaphore or waiting queue 
on file resource? I'm using PHP 4.1.2 and Apache 1.2.23 on Windows platform.

Armin




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[PHP] PHP and DOM XML

[rarmin]

I have one question about operations that can be done with XML.
What I need to do is build a web site which stores some data in XML 
files and retrieve that data. It's basically the system that allows 
users to register, login and upload and download some files. It needs to 
  use XML.

The question is:
If there are simultaneos approaches to register or upload (registration 
and upload data are all stored in the single XML file), using DOM will 
make me problems. DOM loads the whole document into memory, and writes 
it whole to disk. The question is how to avoid this? Since if, for 
example, two users register at the same time, they both get their copy 
of document, and the later that writes itself to the file will overwrite 
the changes made by the first one. How to avoid this and still use DOM? 
I am using PHP 4.1.2 and libxml 2.4.19.

Any advice is wellcome.
Tnx in advance.

Armin


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