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shmop_size> <shmop_open
[edit] Last updated: Sat, 12 May 2012

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(PHP 4 >= 4.0.4, PHP 5)

shmop_readRead data from shared memory block


string shmop_read ( int $shmid , int $start , int $count )

shmop_read() will read a string from shared memory block.



The shared memory block identifier created by shmop_open()


Offset from which to start reading


The number of bytes to read

Return Values

Returns the data or FALSE on failure.


Example #1 Reading shared memory block


This example will read 50 bytes from shared memory block and place the data inside $shm_data.

See Also

shmop_size> <shmop_open
[edit] Last updated: Sat, 12 May 2012
add a note add a note User Contributed Notes shmop_read
Milan Cvejic 18-Feb-2009 01:35
You should always serialize data written in shared memory.
And when you are reading data you should always unserialize.


= 'test';
$shm_bytes_written = shmop_write($shm_id, serialize($data), 0);
$shm_data = unserialize(shmop_read($shm_id, 0, $shm_bytes_written));
Craig Manley 07-Jan-2005 02:19
shmop_read() reads and returns the whole memory segment's data. This is not useful if you're just working with strings. If you need to read a string from shared memory, call str_from_mem() on the result of shmop_read(). Similarly when writing strings to memory (instead of binary data), null terminate your strings with str_to_nts() before passing the value on to shmop_write().

function str_to_nts($value) {
  return "$value\0";

function str_from_mem(&$value) {
  $i = strpos($value, "\0");
  if ($i === false) {
    return $value;
  $result =  substr($value, 0, $i);
  return $result;
slavapl at mailandnews dot com 02-May-2001 12:15
Also you can use the shmop_size() function to determine the block size.
macmaster at pobox dot com 30-Mar-2001 12:01
When i need to read the whole string at that shm pointer, setting the count parameter to zero (0) seems work for me.

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