On thing you might want to do is replace an old string with a shorter one, or to clear out the string altogether.
To replace the string, you can zero-byte pad the string you are writing:
<?php
// $shmid is from shmop_open()
$size = 128;
$string = 'something';
// write
$string = str_pad(string, $size, "\0");
shmop_write($shmid, $string, 0);
// read
print rtrim(shmop($shmid,0,0),,"\0");
// clear
$string = str_repeat("\0",$size);
shmop_write($shmid, $string, 0);
?>
shmop_write
(PHP 4 >= 4.0.4, PHP 5, PHP 7)
shmop_write — Write data into shared memory block
설명
int shmop_write
( resource
$shmid
, string $data
, int $offset
)shmop_write() will write a string into shared memory block.
인수
-
shmid -
The shared memory block identifier created by shmop_open()
-
data -
A string to write into shared memory block
-
offset -
Specifies where to start writing data inside the shared memory segment.
반환값
The size of the written data, or FALSE on
failure.
예제
Example #1 Writing to shared memory block
<?php
$shm_bytes_written = shmop_write($shm_id, $my_string, 0);
?>
This example will write data inside $my_string into shared memory block, $shm_bytes_written will contain the number of bytes written.
add a note
User Contributed Notes 2 notes
mark at manngo dot net ¶
2 years ago
radupb at yahoo dot com ¶
4 years ago
I guess pack-unpack are the handy functions for encoding/decoding data as/from a binary string for shmop_write/shmop_read. Example:
$format='LLLLSSCCCC'; //data format for pack
$key=1;
if( !($shmid=shmop_open($key,'n',0660,30)) )
die('shmop_open failed.');
//my data to encode:
$hd=array('ALIVE1'=>1,'ALIVE2'=>2,'ALIVE3'=>3,'ALIVE4'=>4,
'CRTPTR'=>5,'CRTSEQ'=>6,
'CTW'=>7,'LOCK'=>8,'PLAY'=>9,'MISS'=>10
);
$tmp=pack( $format, $hd['ALIVE1'],$hd['ALIVE2'],$hd['ALIVE3'],$hd['ALIVE4'], $hd['CRTPTR'],$hd['CRTSEQ'],$hd['CTW'],$hd['LOCK'],$hd['PLAY'],$hd['MISS'] );
if( ($w=shmop_write($shmid,$tmp,0))!=24 )
die('write error $w='.$w);
And reading from some other process:
$key=1;
if( !($shmid=shmop_open($key,'w',0,0)) )
die('shmop_open failed.');
$formatR='L4ALIVE/SCRTPTR/SCRTSEQ/CCTW/CLOCK/CPLAY/CMISS'; //data format for unpack
$hd=unpack( $formatR, shmop_read( $shmid,0,24) );
echo'hd:<pre>';print_r($hd);echo'</pre>';
