Not sure if there is a way to check a variable if it is explode-able or not...

I have a database of city names some are one word cities and some are multiple word cities

EX: Chicago, Los Angeles

I keep getting an error when use "implode" when a city name is one word, so I tried using "count" and using an if statement... not having any luck

$citi = explode(' ', $row['city']);
$count = count($citi);
if ($count > 1) {
   $city = implode('+', $citi);
}
else {
   $city = $citi;
}