<?php

$films = [
 "Indiana Jones et le royaume du crâne de cristal" => ["Harrison Ford", "Cate Blanchett", "Karen Allen"],
 "Indiana Jones et la dernière croisade" => ["Harrison Ford", "Sean Connery", "Denholm Elliott"],
 "Indiana Jones et le temple maudit" => ["Harrison Ford", "Kate Capshaw", "Jonathan Ke Quan"]
];

foreach($films as $film => $actors) {
  $allActors = implode(", ", $actors);
  echo "Dans le film $film, les principaux acteurs sont : $allActors";
  echo "<br>";
}

?>