no return from exec("java matchUploadPic")

[yunfong]

hi, i haf faced with a prob which i dunoe y after exec("java matchUploadPic");
e code nvr return as i need to read a file written by from that execution, i CANT READ AT ALL.. it will jus skip it. Can anyone help to check whether did i do wrongly? Thanks!!!

$pFile = $_FILES["file"]["name"];
	echo $pFile."</br>";
        chdir("extractFeatures\siftDemoV4\\");
        storeUpload($pFile);
        $pos = strpos($pFile,".jpg");
        $fileN = substr($pFile,0,$pos);
        chdir("C:\Program Files\IrfanView\\");
        $convert = "cmd /c i_view32.exe D:\YunFong's FYP\Test\PhpProject1\Images from Columbia\\".
        $pFile." /convert=D:\YunFong's FYP\Test\PhpProject1\extractFeatures\siftDemoV4\\".$fileN.".pgm";
        exec($convert);

    chdir("D:\YunFong's FYP\Test\PhpProject1\extractFeatures\siftDemoV4\\");

    $run = "cmd /c siftWin32 <".$fileN.".pgm >".$fileN.".key";
    $wt = fopen("key.txt","w");
    fwrite($wt,$run);
    fclose($wt);
    exec("java key");
    copy($fileN.".pgm",'pics/'.$fileN.".pgm"); //move file to another inner folder (pics folder)
    copy($fileN.".key","pics/".$fileN.".key");
    unlink($fileN.".key");
    unlink($fileN.".pgm");
    chdir("pics\\");

    $match = "cmd /c match -im1 ".$fileN.".pgm -k1 ".$fileN.".key -im2 ";
    $wt2 = fopen("match.txt","w");
    fwrite($wt2,$match);
    fclose($wt2);

    exec("java matchUploadPic");
chdir("..\\");
        //echo getcwd();

    $sortMatch = fopen("detectedMatching_C.txt","r");

    if($sortMatch) {
        while(!feof($sortMatch)) {
            $s = fgets($sortMatch);
            $sort = explode("\t",$s);
            $sortedArr[$a] = $sort;
            $a++;
        }
    }
    fclose($sortMatch);