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, $mutex_key, FALSE); ?>)
It would be nice to have a completely air-tight solution, though. D'oh!
shm_get_var
Description
mixed shm_get_var ( int shm_identifier, int variable_key )shm_get_var() returns the variable with a given variable_key, in the shared memory segment identified by shm_identifier. shm_identifier was obtained from shm_attach(). The variable is still present in the shared memory.
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User Contributed Notes
JM
15-May-2005 06:50
15-May-2005 06:50
06-May-2005 05:01
You will still receive a notice use @:
if(!defined(@shm_get_var($mutex, $mutex_key))) {
shm_put_var($mutex, $mutex_key, 0);
}
Bob Van Zant
18-Feb-2005 04:05
18-Feb-2005 04:05
This seems to work fine to detect the lack of presence of a key in shared memory and then init it to 0 when found:
if(!defined(shm_get_var($mutex, $mutex_key))) {
shm_put_var($mutex, $mutex_key, 0);
}
chris at free-source dot com
06-Dec-2004 06:47
06-Dec-2004 06:47
if the variable_key asked for does not exist php generates a warning and shm_get_var() will return bool(false). there doesn't seem to be a clean way to test if a key exists.