Read data from shared memory block

shmop_read(Shmop $shmop, int $offset, int $size): string

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

shmop: The shared memory block identifier created by shmop_open()
offset: Offset from which to start reading; must be greater than or equal to zero and less than or equal to the actual size of the shared memory segment.
size: The number of bytes to read; must be greater than or equal to zero, and the sum of offset and size must be less than or equal to the actual size of the shared memory segment. 0 reads shmop_size($shmid) - $start bytes.

Returns the data 或者在失败时返回 false.

If offset or size are out of range, a ValueError is thrown.

版本	说明
8.0.0	`shmop` expects a Shmop instance now; previously, a resource was expected.
8.0.0	If `offset` or `size` are out of range, a ValueError is thrown; previously `E_WARNING` was emitted, and `false` was returned,

示例 #1 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.