(PHP 4, PHP 5, PHP 7, PHP 8)
shm_get_var — Returns a variable from shared memory
shm_get_var() returns the variable with a given
key, in the given shared memory segment.
The variable is still present in the shared memory.
Returns the variable with the given key.
If any body has problem with shm_get_var();
this code correctly work with boolean-values^
<?php
if(shm_has_var ($this->shm_mem_id, $_varno)){
$_value = shm_get_var($this->shm_mem_id, $_varno);
}else{
$_value = NULL;
}
?>
hello everyone i came up with some sort of solution to the shm_get_var()
returns false on error/returns a boolean false variable problem.
test script
<?php
error_reporting(E_ALL);
ini_set('display_errors', '1');
echo '<pre>';
echo ini_get('sysvshm.init_mem');
require_once('ClassShmWrapper.php5');
$nKey = ftok(__FILE__,'x');
$myShm = new ClassShmWrapper($nKey);
$myShm->attachToSegment();
#$mValue = range(1,rand(3,10));
#$myShm->nVarKey = count($mrValue);
#$mValue = FALSE;
/*
$mValue = TRUE;
$myShm->nVarKey = 1;
$myShm->mVar = $mValue;
$myShm->putVarToSegment();
*/
#$myShm->nVarKey = 2;
$myShm->nVarKey = 1;
if ($myShm->getVarFromSegment()) {
echo "found var in shm\n";
}
else {
echo "could NOT find var in shm\n";
}
$myShm->detachFromSegment();
echo "\ndumping " . '$myShm->mVar' . "\n";
var_dump($myShm->mVar);
?>
class for using the shm_ functions & class for storing boolean values
<?php
class ClassShmWrapper {
public $nPermissions;
public $nKey;
public $nBytesMemorySize;
public $nShmId;
public $nVarKey;
public $mVar;
public function __construct($nKey,$nBytesMemorySize=50000,$nPermissions=0666) {
$this->nKey = $nKey;
$this->nBytesMemorySize = $nBytesMemorySize;
$this->nPermissions = $nPermissions;
}
public function attachToSegment() {
$this->nShmId = shm_attach($this->nKey,$this->nBytesMemorySize,$this->nPermissions);
}
public function detachFromSegment() {
shm_detach($this->nShmId);
}
public function removeSegment() {
shm_remove($this->nShmId);
}
public function getVarFromSegment() {
$mVar = NULL;
if (($mVar = @shm_get_var($this->nShmId,$this->nVarKey)) !== FALSE) {
$this->mVar = $mVar;
unset($mVar);
/*
For variables of type boolean we need to access an object property which stores the boolean value.
This is needed as shm_get_var() could return FALSE when returning a boolean variable set to FALSE
or when a non-existing variable key was tried to access!
*/
if ($this->mVar instanceof ClassShmBooleanWrapper) {
$this->mVar = $this->mVar->bVal;
}
return TRUE;
}
else {
return FALSE;
}
}
/**
* Puts a PHP variable into shared memory (or updates an existing one for the given variable key).
*
* @return boolean returns TRUE on success/FALSE on error
*/
public function putVarToSegment() {
// cmp -> comment getVarFromSegment()
if (is_bool($this->mVar)) {
return shm_put_var($this->nShmId,$this->nVarKey,new ClassShmBooleanWrapper($this->mVar));
}
else {
return shm_put_var($this->nShmId,$this->nVarKey,$this->mVar);
}
}
public function removeVarFromSgement() {
shm_remove_var($this->nShmId,$this->nVarKey);
}
} // end class
class ClassShmBooleanWrapper {
public $bVal;
public function __construct($bVal) {
$this->bVal = $bVal;
}
} // end class
?>
I was annoyed by this warning when using shm_get_var():
Warning: shm_get_var() [function.shm-get-var]: variable key 2 doesn't exist in PATH_TO_FILE on line 64.
You can suppress the warning by changing the error reporting level. To do this for just the page in question, include the following line:
<?php
error_reporting(E_ERROR);
?>
For more info: http://us.php.net/error_reporting
A fully functional sample ...
<?php
echo "<PRE>\n";
define("FOPEN_RESOURCE", 1);
$shm_id = shm_attach(FOPEN_RESOURCE);
if ($shm_id === false) {
exit("Fail to attach shared memory.\n");
}
$fopen_resource = fopen("/tmp/phpSharedMemory.bin", "w");
$a = array("Teste1", 1);
if (!shm_put_var($shm_id, $a, $a)) {
exit("Failed to put var 1 in shared memory $shm_id.\n");
}
echo "F: ".$a[0].":".$a[1]."\n";
$pid = pcntl_fork();
if($pid == -1) {
die("could not fork\n");
}
else if ($pid) {
$a = array("Teste2", 3);
if (!shm_put_var($shm_id, $a, $a)) {
exit("Failed to put var 1 in shared memory $shm_id.\n");
}
echo "P1: ".$a[0].":".$a[1]."\n";
} else {
sleep(2);
$a = shm_get_var($shm_id, $a);
echo "P2: ".$a[0].":".$a[1]."\n";
}
pcntl_wait($status);
exit();
?>
To follow up on the posts by anonymous, Bob Van Zant and chris at free-source dot com below (or, as must people inexplicably write, above) regarding the PHP warning and FALSE that shm_get_var returns if the variable key doesn't exist:
My tests (with PHP4.3.4) show that defined() is useless here. Because the function defined(string) checks whether the constant whose name is string exists, the code
<?php
if ( defined(@shm_get_var($mutex, $mutex_key)) {
...
}
?>
acts the same ("..." does not get executed) whether the variable is defined or not--unless $mutex_key happens to identify a valid string that happens to be the name of a constant. :)
Rather,
<?php
if ( @shm_get_var($mutex, $mutex_key) === FALSE ) {
...
}
?>
works, provided the object that was stored isn't actually FALSE (via <?php shm_put_var($mutex, $mutex_key, FALSE); ?>)
It would be nice to have a completely air-tight solution, though. D'oh!
You will still receive a notice use @:
if(!defined(@shm_get_var($mutex, $mutex_key))) {
shm_put_var($mutex, $mutex_key, 0);
}
This seems to work fine to detect the lack of presence of a key in shared memory and then init it to 0 when found:
if(!defined(shm_get_var($mutex, $mutex_key))) {
shm_put_var($mutex, $mutex_key, 0);
}