10.2.1. Problem

10.2.2. Solution

$data_file = '/tmp/data';

// open the file for reading and writing
$fh = fopen($data_file,'a+') or die($php_errormsg);
rewind($fh)                  or die($php_errormsg);

// get an exclusive lock on the file 
flock($fh,LOCK_EX)           or die($php_errormsg);

// read in and unserialize the data
$serialized_data = fread($fh,filesize($data_file)) or die($php_errormsg);
$data = unserialize($serialized_data);

/*
 * do whatever you need to with $data ...
 */

// reserialize the data 
$serialized_data = serialize($data);

// clear out the file
rewind($fh)                  or die($php_errormsg);
ftruncate($fp,0)             or die($php_errormsg);

// write the data back to the file and release the lock 
if (-1 == (fwrite($fh,$serialized_data))) { die($php_errormsg); }
fflush($fh)                  or die($php_errormsg);
flock($fh,LOCK_UN)           or die($php_errormsg);
fclose($fh)                  or die($php_errormsg);

10.2.3. Discussion

10.2.4. See Also