print_r(variable, return); // second parameter is optional
For instance:
$cars = array("BMW", "Ferrari", "Mustang");
print_r($cars);
$names = array("Keira Knightley"=>"37", "Mads Mikkelsen"=>"56", "Keanu Reeves"=>"58");
print_r($names);
/* outputs:
Array
(
[0] => BMW
[1] => Ferrari
[2] => Mustang
)
Array
(
[Keira Knightley] => 37
[Mads Mikkelsen] => 56
[Keanu Reeves] => 58
)
*/