File lock - warning ?

I open a file in append mode, I locked it and write the data.
But when I try to unlock or close it then I get warning

Warning: Unable to find file identifier 12 in www/htdocs/testfclose.php3 on 
line 9

Warning: Unable to find file identifier 12 in  www/htdocs/testfclose.php3 
on line 10
close ok

I am using PHP3 - code
------------------------------------------------
echo "start";
$fpLog = fopen 
("/usr/home/aurica/aurica.com/cannesEmail/emailblastSendLog.txt","a");

if (flock ($fpLog, 2) ) {
        $strFileLog = "Manisha Test";
        $fpLog = fwrite("$fpLog",$strFileLog);
}
$tmp = flock ($fpLog, 3);
fclose ($fpLog);
echo "close ok ";
------------------------------------------------

What's wrong ?

Thanks in advance,
Manisha