Something

<?php

$arr = file('links.txt');
$arr2 = file('final.txt');
$newArray = array_unique($arr);
foreach($newArray as $line) { 
$k++;
$split = explode('&dealer_id=', rtrim($line)); 

$fop = fopen('final.txt',"a");
fwrite($fop,$split[0] . " : " . $split[1]."\r\n");
}

	if($k==count($newArray)){
		fclose($fop);
		//////////////////////////////////////////////////////////////////////////////
			foreach($arr2 as $lines) { 
			$f++;
			print $f . "<br>";
			$splitz = explode(':', rtrim($lines));
			$fopo = fopen('done.txt',"a");
				if(strpos(file_get_contents('done.txt'),$splitz[1])===false){
					fwrite($fopo,$splitz[0] . " : " . $splitz[1]."\r\n");
				} 
				if($f==count($arr2)){
					fclose($fopo);
					exit();
				}
			}
		//////////////////////////////////////////////////////////////////////////////
	}


?>