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# CXL. Shared Memory Functions

# Introduction

Shmop is an easy to use set of functions that allows PHP to read, write, create and delete Unix shared memory segments.

> Note: Versions of Windows previous to Windows 2000 do not support shared memory. Under Windows, Shmop will only work when PHP is running as a web server module, such as Apache or IIS (CLI and CGI will not work).

> Note: In PHP 4.0.3, these functions were prefixed by shm rather than shmop.

# Requirements

No external libraries are needed to build this extension.

# Installation

To use shmop you will need to compile PHP with the --enable-shmop parameter in your configure line.

# Runtime Configuration

This extension has no configuration directives defined in `php.ini`.

# Resource Types

# Predefined Constants

This extension has no constants defined.

# Examples

Example 1. Shared Memory Operations Overview
`<?php // Create 100 byte shared memory block with system id of 0xff3 $shm_id = shmop_open(0xff3, "c", 0644, 100); if (!$shm_id) { echo "Couldn't create shared memory segment\n"; } // Get shared memory block's size $shm_size = shmop_size($shm_id); echo "SHM Block Size: " . $shm_size . " has been created.\n"; // Lets write a test string into shared memory $shm_bytes_written = shmop_write($shm_id, "my shared memory block", 0); if ($shm_bytes_written != strlen("my shared memory block")) { echo "Couldn't write the entire length of data\n"; } // Now lets read the string back $my_string = shmop_read($shm_id, 0, $shm_size); if (!$my_string) { echo "Couldn't read from shared memory block\n"; } echo "The data inside shared memory was: " . $my_string . "\n"; //Now lets delete the block and close the shared memory segment if (!shmop_delete($shm_id)) { echo "Couldn't mark shared memory block for deletion."; } shmop_close($shm_id); ?>`

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