php 多线程上下文中安全写文件实现代码

提供一个php多线程上下文中安全写文件的实现方法。这个实现没有使用php 的file lock机制，使用的是临时文件机制。多线程中的各个线程都是对各自（每个线程独占一个）的临时文件写，然后再同步到原文件中。

 
<?php 
/** 
* @usage: used to offer safe file write operation in multiple threads context, arbitory file type 
* @author: Rocky Zhang 
* @time: Nov. 11 2009 
* @demo[0]: $handler = mfopen($file, 'a+'); 
* mfwrite($handler, $str); 
*/ 
function mfopen($file, $mode='w+') { 
$tempfile = generateTempfile('./tempdir', $file); 
preg_match('/b/i', $mode) || ($mode .= 'b'); // 'b' is recommended 
if (preg_match('/\w|a/i', $mode) && !is_writable($file)) { 
exit("{$file} is not writable!"); 
} 
$filemtime = $filemtime2 = 0; 
$tempdir = dirname($tempfile); 
is_dir($tempdir) || mkdir($tempdir, 0777); 
do { // do-while used to avoid modify in a long time copy 
clearstatcache(); 
$filemtime = filemtime($file); 
copy($file, $tempfile); 
$filemtime2 = filemtime($file); 
} while ( ($filemtime2 - $filemtime) != 0 ); 
if (!$handler = fopen($tempfile, $mode)) { 
exit('Fail on opening tempfile, write authentication is must on temporary dir!'); 
} 
return array(0=>$handler, 1=>$filemtime, 2=>$file, 3=>$tempfile, 4=>$mode); 
} 

// I do think that this function should be optimized further 
function mfwrite(&$handler, $str='') { 
if (strlen($str) > 0) { 
$num = fwrite($handler[0], $str); 
fflush($handler[0]); 
} 
clearstatcache(); 
$mtime = filemtime($handler[2]); 
if ( $mtime == $handler[1] ) { // compare between source file and temporary file 
if ( $num && $num > 0 ) { // temporary file has been updated, copy to source file 
copy($handler[3], $handler[2]) || exit; 
$handler[1] = filemtime($handler[3]); 
touch($handler[2], $handler[1], $handler[1]); 
} 
} else { // source file has been modified, load source file to temporary file 
copy($handler[2], $handler[3]) || exit; 
touch($handler[3], $mtime, $mtime); 
$handler[1] = $mtime; 
} 
} 

function generateTempfile($tempdir='tempdir', $file) { 
$rand = md5(microtime()); 
return "{$tempdir}/{$rand}_".$file; 
} 
?>