Duplicate entry condition for mysql data base

When I want to write duplicate entry to a UNIQUE column in mysql I get the error Duplicate entry '' for key 'UNIQUE' . Is it possible to use this error as a condition for if() statement in PHP? I use code below to insert entry in column.

$s = "INSERT INTO `table`(`entry`)
if ($conn->query($s) === TRUE) {
      echo "New record created successfully";
    } else {
      echo "Error: " . $s . "<br>" . $conn->error;
    }