<?php
 
$firstname = array ( "John", "Tom", "Ben", "John", "David", "Julie", "David");
$lastname = array ("Kennedy", "Hyde", "Hughes", "Harper", "Walter", "Weber", "Walter");
$fullname = array();
$duplicates = array();
for ($i =0; $i < count($firstname); $i++){
	$fullname_tmp = $firstname[$i]." ".$lastname[$i];
	if (in_array($fullname_tmp, $fullname)){
		if (in_array($duplicates, $fullname_tmp)){
			$duplicates[] = $fullname_tmp;
		}
		else{
			$duplicates[] = $fullname_tmp;
			$duplicates[] = $fullname_tmp;
		}
 
	}
	else{
		$fullname[] = $fullname_tmp;
	}
}
 
echo "<pre>\n duplicates \n";
 
print_r($duplicates);
 
echo "\n full names \n";
 
print_r($fullname);

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