shmop_read()

(PHP 4 >= 4.0.4, PHP 5, PHP 7)

Read data from shared memory block

说明

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

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

参数

$shmid

The shared memory block identifier created by shmop_open()

$start

Offset from which to start reading

$count

The number of bytes to read.0readsshmop_size($shmid)- $startbytes.

返回值

Returns the data 或者在失败时返回FALSE.

更新日志

范例

Reading shared memory block

<?php
$shm_data = shmop_read($shm_id, 0, 50);
?>

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

参见

• shmop_write()Write data into shared memory block

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;
}

When i need to read the whole string at that shm pointer, setting the count parameter to zero (0) seems work for me.

Also you can use the shmop_size() function to determine the block size.

You should always serialize data written in shared memory.
And when you are reading data you should always unserialize.
<?php
$data = 'test';
$shm_bytes_written = shmop_write($shm_id, serialize($data), 0);
$shm_data = unserialize(shmop_read($shm_id, 0, $shm_bytes_written));
?>