Question

$foo = '';

foreach((array)$foo as $f){
  echo 'xxx';
}

Will still output ‘xxx’…

Answer 1

Casting an empty string to an array won’t result in an empty array. It will create an array with an empty string as an item:

array(
    0 => ''
)

You could check if it’s a valid array:

if(is_array($foo))
{
    foreach($foo as $f)
    {
        echo 'xxx';
    }
}