Batch Downloading in PHP

<?php
for($d=1;$d<=100;$d++)
{
$link="http://www.domain.com/demos/".$d."/source.zip";
if(http_url_exists($link))
{
  echo"Processing: ".$link."<br>";
  
  exec("wget -O ".dirname(__FILE__)."/download/source-".$d.".zip ".$link." 2>&1",$pp);
  
  echoimplode("",$pp);echo"<br><br>";
}
}
//$file_headers = @get_headers($file);
//'HTTP/1.1 404 Not Found'
 
function url_exists($url){
    if(!$fp=curl_init($url))returnfalse;
    returntrue;
}
function http_url_exists($url){
    
    $file_headers=@get_headers($url);
    
    if($file_headers[0]=='HTTP/1.1 404 Not Found')
        returnfalse;
    
    returntrue;
}
?>