#Dummy initial filehandle to obtain lock via 
$fd = fopen('c:/temp/php_flock_test', 'a'); 

$locked = flock($fd,2); #Exclusive blocking lock 
if (!$locked) { 
print "Error: timeout obtaining lock"; exit; 
} 

#Second (actually used) filehandle 
$fdsafe = fopen('c:/temp/php_flock_test', 'w'); 
fwrite($fdsafe,'Replacement text'); 
fclose($fdsafe); 

fclose($fd); 

//================= 

// This will simply create the file but not put "Replacement text" in the file.