how to extract texts from PDFs using xpdf?

I have many PDFs in a folder. I want to extract the text from these PDFs using xpdf. For example :

• example1.pdf extract to example1.txt
• example2.pdf extract to example2.txt
• etc..

here is my code :

<?php

$path = 'C:/AppServ/www/pdfs/';
$dir = opendir($path);
$f = readdir($dir);

while ($f = readdir($dir)) {
    if (eregi("\.pdf",$f)){
        $content = shell_exec('C:/AppServ/www/pdfs/pdftotext '.$f.' ');
        $read = strtok ($f,".");
        $testfile = "$read.txt";
        $file = fopen($testfile,"r");
        if (filesize($testfile)==0){} 
        else{
           $text = fread($file,filesize($testfile));
        fclose($file);
        echo "</br>"; echo "</br>";
        }
    }
}

I get blank result. What's wrong with my code?

try using this :

$dir      = opendir($path);
$filename = array();

while ($filename = readdir($dir)) {
if (eregi("\.pdf",$filename)){
    $content  = shell_exec('C:/AppServ/www/pdfs/pdftotext '.$filename.' ');
    $read     = strtok ($filename,".");
    $testfile = "$read.txt";
    $file     = fopen($testfile,"r");
    if (filesize($testfile)==0){} 
    else{
        $text = fread($file,filesize($testfile));
        fclose($file);
        echo "</br>"; echo "</br>";
    }
}