search intersection array

<?php
$a = array(5,6,7);
$b = array(1,2,3,4);
$c = array(1,2,3);

echo '<br','>$a,$b: ';
if (count(array_intersect($a,$b)) > 0){
 echo 'duplicate ', var_export(array_intersect($a,$b),true);
} else {
 echo 'not duplicate'; 
}

echo '<br','>$b,$c: ';
if (count(array_intersect($b,$c)) > 0){
 echo 'duplicate ', var_export(array_intersect($b,$c),true);
} else {
 echo 'not duplicate'; 
}

?>