int shmop_open (int key, string flags, int mode, int size)
shmop_open() can create or open a shared memory block.
shmop_open() takes 4 parameters: key, which is the system's id for the shared memory block, this parameter can be passed as a decimal or hex. The second parameter are the flags that you can use:
The third parameter is the mode, which are the permissions that you wish to assign to your memory segment, those are the same as permission for a file. Permissions need to be passed in octal form ex. 0644. The last parameter is size of the shared memory block you wish to create in bytes.
Note: Note: the 3rd and 4th should be entered as 0 if you are opening an existing memory segment. On success shmop_open() will return an id that you can use to access the shared memory segment you've created.
Example 1. Create a new shared memory block
<?php $shm_id = shmop_open(0x0fff, "c", 0644, 100); ?>
This example opened a shared memory block with a system id of 0x0fff.