shmop_delete
If you faced with any problem you're going to solve with shared memmory, but your server doesn't support it, you can use files instead. I've wrote simple wrapper for this and its suites for me. Hope it will be usefull for you too.
<?php
define(kSHARED_FOLDER, "shared/");
define(kSHARED_MAX_ATTEMPS, 10);
define(kSESSION_SHARED, "shared_");
class Shared {
var $id = 0;
var $filename = '';
var $filepointer;
var $data = array();
var $date = 0;
function Shared($id) {
$this->id = $id;
$this->filename = kSHARED_FOLDER.$this->id;
if(empty($this->filename))
{
print "no filename";
return false;
}
$this->date = $_SESSION[kSESSION_SHARED.$id];
}
function clear() {
if ($this->id == null)
{
return false;
}
$counter = 0;
ignore_user_abort(true);
if(($this->filepointer = @fopen($this->filename, "w")) == false) {
ignore_user_abort(false);
return false;
}
while(true) {
if ($counter >= kSHARED_MAX_ATTEMPS) {
fclose($this->filepointer);
ignore_user_abort(false);
return false;
}
if(flock($this->filepointer, LOCK_EX) == false) {
$counter++;
usleep(rand(1, 25000));
}
else
break;
}
if(flock($this->filepointer, LOCK_UN) == false) {
ignore_user_abort(false);
return false;
}
unset($this->data);
$this->data = array();
fclose($this->filepointer);
$this->date = $_SESSION[kSESSION_SHARED.$id] = filemtime($this->filename);
ignore_user_abort(false);
return true;
}
function setObjectForKey($value, $key) {
if ($this->id == null)
return false;
$counter = 0;
ignore_user_abort(true);
if(($this->filepointer = @fopen($this->filename, "a+")) == false) {
ignore_user_abort(false);
print "can not open file<br>";
return false;
}
while(true) {
if ($counter >= kSHARED_MAX_ATTEMPS) {
fclose($this->filepointer);
print("1 aborted...");
ignore_user_abort(false);
return false;
}
$block;
if(flock($this->filepointer, LOCK_EX, $block) == false) {
$counter++;
print("1 waiting...");
usleep(rand(1, 25000));
}
else
break;
}
$data = file_get_contents($this->filename);
$array = array();
if (!empty($data))
$array = unserialize($data);
$array[$key] = $value;
$data = serialize($array);
ftruncate($this->filepointer, 0);
fseek($this->filepointer, 0, SEEK_SET);
fwrite($this->filepointer, $data);
$this->data = $array;
if(flock($this->filepointer, LOCK_UN) == false) {
ignore_user_abort(false);
return false;
}
fclose($this->filepointer);
$this->date = $_SESSION[kSESSION_SHARED.$id] = filemtime($this->filename);
ignore_user_abort(false);
return true;
}
function getObjectForKey($key) {
if ($this->id == null)
return null;
$counter = 0;
ignore_user_abort(true);
if(($this->filepointer = @fopen($this->filename, "a+")) == false) {
ignore_user_abort(false);
print("can not open<br>");
return null;
}
if ($this->date == filemtime($this->filename)) {
fclose($this->filepointer);
return $this->data[$key];
}
while(true) {
if ($counter >= kSHARED_MAX_ATTEMPS) {
fclose($this->filepointer);
ignore_user_abort(false);
print("2 aborted<br>");
return null;
}
if(flock($this->filepointer, LOCK_SH ) == false) {
$counter++;
print("2 waiting...<br>");
usleep(rand(1, 25000));
}
else
break;
}
fseek($this->filepointer, 0);
$data = file_get_contents($this->filename);
$array = array();
if (!empty($data))
$array = unserialize($data);
$data = $array[$key];
$this->data = $array;
if(flock($this->filepointer, LOCK_UN) == false) {
ignore_user_abort(false);
return $data;
}
fclose($this->filepointer);
$this->date = $_SESSION[kSESSION_SHARED.$id] = filemtime($this->filename);
ignore_user_abort(false);
return $data;
}
}
?>
shmop_open
(PHP 4 >= 4.0.4, PHP 5)
shmop_open — Crea o abre un segmento de memoria compartida
Descripción
int shmop_open
( int $clave
, string $opciones
, int $modo
, int $tamanio
)
shmop_open() se utiliza para crear o abrir un segmento de memoria compartida.
shmop_open() utiliza 4 parametros: clave, que es el identificador que el sistema utilizará para ese segmento de memoria compartida y que puede ser indicado tanto en formato decimal como hexadecimal. El segundo parámetro son las opciones que se pueden utilizar:
- "a" para acceder (se activa SHM_RDONLY en el shmat) se utiliza esta opción para abrir un segmento de memoria compartida que ya existe en modo de solo lectura.
- "c" para crear (se activa IPC_CREATE) se utiliza esta opción para crear un nuevo segmento de memoria compartida o para intentar abrir en modo de lectura y escritura un segmento que ya existe.
- "w" para acceder en modo de lectura y escritura. Se utiliza esta opción para poder leer un segmento de memoria compartida y además poder escribir en el. Se trata de la opción más habitual en la mayoría de los casos.
- "n" para crear un nuevo segmento de memoria compartida (se activan IPC_CREATE|IPC_EXCL) se utiliza esta opción para crear un nuevo segmento de memoria compartida a no ser que ya exista otro segmento de memoria compartida con la misma clave. Esta opción es útil por motivos de seguridad para evitar por ejemplo "condiciones de carrera" (en inglés "race conditions").
Note: Nota: el tercer y cuarto parámetro deben ser igual a 0 (cero) si se está abriendo un segmento de memoria compartida existente. Si la función shmop_open() tiene éxito, devolverá un identificador que se puede utilizar posteriormente para acceder al segmento de memoria compartida que se ha creado.
Example #1 Creación de un nuevo segmento de memoria compartida
<?php
$shm_key = ftok(__FILE__,'t');
$shm_id = shmop_open($shm_key, "c", 0644, 100);
?>
En el ejemplo anterior se crea un nuevo segmento de memoria compartida cuya clave se ha generado con ayuda de la función ftok().
add a note
User Contributed Notesshmop_open
DinosauRUS
29-Aug-2008 12:24
29-Aug-2008 12:24
erelsgl at gmail dot com
27-Nov-2007 12:04
27-Nov-2007 12:04
=== Checking if a shared memory exists ===
The solution provided by Mitchell_Shnier at ieee dot orgZ doesn't work on my computer - I get a warning "Invalid flag ac".
In order to check if a shared-memory exists, you just have to open it with the "a" or "w" flag, while hiding the warnings using the "@" operator:
<?php
@$shid = shmop_open($systemId, "a", 0666, 0);
if (!empty($shid)) {
... shared memory exists
} else {
... shared memory doesn't exist
}
?>
Craig Manley
06-Jan-2005 02:19
06-Jan-2005 02:19
To: macmaster at pobox dot com:
To clear up some new confusion: you said the shm key is 8 bytes long. As far as I know it's 4 bytes (32bits).
Check out the output of ipcs on Linux below to see what I mean.
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x6e6a694d 65538 mijnbel 644 65536 0
0x326e794d 98307 mijnbel 644 65536 0
0x62417347 131076 smsklap 644 65536 0
me at here dot com
08-Dec-2004 02:04
08-Dec-2004 02:04
Just an alternative idea if 'shared memory' is what you need for your websites, you can use tmpfs (on Linux):
Get root to do this:
mkdir /home/myname/tmpfs
chown myname:mygroup /home/myname/tmpfs
..and this in a script executed at boot time:
mount -t tmpfs /mnt/tmpfs /home/myuser/tmpfs
Now you can use regular file functions (including locking) to access shared memory between all your processes.
More info: http://docsun.cites.uiuc.edu/sun_docs/C/
...and this because the note editor doesn't accept long lines...
solaris_9/SUNWaadm/SYSADV1/p150.html
daniele_dll at yahoo dot it
01-Feb-2004 10:28
01-Feb-2004 10:28
There is a little ftok function. This function isn't included into php for windows so i've grabbed it directly from linux glibc 2.3.2 source code. I hope that this can be useful.
There is the code:
<?php
function ftok($pathname, $proj_id) {
$st = @stat($pathname);
if (!$st) {
return -1;
}
$key = sprintf("%u", (($st['ino'] & 0xffff) | (($st['dev'] & 0xff) << 16) | (($proj_id & 0xff) << 24)));
return $key;
}
echo ftok($_SERVER["SCRIPT_FILENAME"], 250);
?>
sorry for my english :)
Chris Petersen
28-Aug-2003 08:18
28-Aug-2003 08:18
Be warned that if you try to shmop_open with a key set to zero, shmop_open will seemingly work, and you can write to it, but you will not be able to read from it or delete it. If you're not careful, you can continue doing this - creating more and more shared memory blocks at "zero" until eventually you WILL start getting errors saying that php can't access or create the shared memory block, and you will have to restart your machine to free up all of those "zero" blocks.
Mitchell_Shnier at ieee dot orgZ
08-Nov-2001 02:51
08-Nov-2001 02:51
To check whether a particular shared memory segment is already created, you need to concatenate the "a" and "c" flags. For example (where $SystemKey is the Unix key used by the other process(es) with which you want to share this memory segment)...<BR>
$shm_id = shmop_open($SystemKey, "ac", 0, 0);
if ($shm_id) {
#it is already created
} else {
#you need to create it with shmop_open using "c" only
}<BR>
Using only "a" does not work (just as using only IPC_EXCL in the Unix shmget() call is meaningless). Also, use the ipcs shell command to see your shared memory segments.
macmaster at pobox dot com
30-Mar-2001 10:15
30-Mar-2001 10:15
the key is a LONG variable type, meaning that the key can only be eight (8) bytes long, which can be too short if you're using any form of automagic key generation (like a parsed filename)