Need help updating PHP script that counts duplicate emails in 2 uploaded CSV files

I've been asked to revise to a custom PHP script that I developed for someone (about a year ago) that counts duplicate email addresses that are in 2 uploaded CSV files.    

Right now, if there are duplicates in list #1, it reports those dupes.  What I need to do is update it so that it only reports the duplicates that are BETWEEN the two lists - and NOT the duplicates that are within either list.  

I thought that it'd be quick and easy, but I can't seem to figure it out. I'm thinking there might some way to filter the dupes out of each of the CSV files individually before I merge them, perhaps?

My PHP code and is below, and some sample CSV files are attached.  Any help would be appreciated.

Thanks!
- Yvan

<?php		
	
	$csv1filename = $_FILES['csv1']['tmp_name'];

	$ext1 = strtoupper(pathinfo($_FILES['csv1']['name'], PATHINFO_EXTENSION));							
	
	$csv2filename = $_FILES['csv2']['tmp_name'];
	
	$ext2 = strtoupper(pathinfo($_FILES['csv2']['name'], PATHINFO_EXTENSION));		

	if ($ext1 == 'CSV' && $ext2 == 'CSV')	{	

		$csv1 = '/home/expert/public_html/dupes/csv1.csv';					

		move_uploaded_file($csv1filename, $csv1);

		$csv2 = '/home/expert/public_html/dupes/csv2.csv';	

		move_uploaded_file($csv2filename, $csv2);					

		// CREATE THE EMPTY ARRAY
		
		$raw_array = array();				
		
		$csv1 = file($csv1, FILE_IGNORE_NEW_LINES + FILE_SKIP_EMPTY_LINES);
		
		$csv2 = file($csv2, FILE_IGNORE_NEW_LINES + FILE_SKIP_EMPTY_LINES);

		$raw_array = array_merge($csv1, $csv2); 					
		
		// FUNCTION TO COUNT DUPLICATE EMAILS IN THE ARRAY
		
		function array_not_unique($raw) {
			$new = array_count_values($raw);				
			foreach ($new as $key => $val) {
			   if ($val < 2) unset($new[$key]);
			}				
			return $new;				
		}		

		$common = array_not_unique($raw_array);

		// DELETE EXPORT CSV FILE IF IT ALREADY EXISTS	

		if ( file_exists("/home/expert/public_html/dupes/duplicates.csv") ) {
			unlink ("/home/expert/public_html/dupes/duplicates.csv");
		}	
		
		// OPEN FILE FOR WRITING AND ADD COLUMN HEADERS
		
		$fd = fopen("/home/expert/public_html/dupes/duplicates.csv", "a");
		
		fwrite($fd, "EMAIL\n");				

		// DISPLAY THE NUMBER OF DUPES FOUND IN THE ARRAY
		
		$total = 0;
		
		echo "<pre style='text-align:left;line-height:45px;'>";					
		
		foreach ($common as $x => $n) {
			
			$total++;							
			
			// LOOP THROUGH DATA AND APPEND DUPLICATE EMAILS TO CSV FILE					

			fwrite($fd, $x . "\n");	
			
		}	
		
		// CLOSE THE FILE
		
		fclose($fd);
		
		echo "</pre>";
		
		echo "<br />A Total of <strong style='text-align:center;background-color:#FBCB45;padding:3px;'>$total</strong> duplicate email addresses were found.<br /><br /><br />";
		
		echo "Click <strong><a href=\"duplicates.csv\" target=\_blank\">here</a></strong> to download a CSV file which contains<br />the duplicate email addresses<br /><br /><br />";	
						
		echo '<a href="/dupes/" style="font-size:18px;text-decoration:none;font-weight:bold;color:blue;">&lt;&lt; Back</a>';
		
		unlink('/home/expert/public_html/dupes/csv1.csv');
		
		unlink('/home/expert/public_html/dupes/csv2.csv');							

	} else {

		echo 'Improper file type uploaded.';
		
	}	
	
?>	

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sample1.csv
sample2.csv