Why check both isset() and !empty()

This is completely redundant. empty is more or less shorthand for !isset($foo) || !$foo, and !empty is analogous to isset($foo) && $foo. I.e. empty does the reverse thing of isset plus an additional check for the truthiness of a value.

Or in other words, empty is the same as !$foo, but doesn't throw warnings if the variable doesn't exist. That's the main point of this function: do a boolean comparison without worrying about the variable being set.

The manual puts it like this:

empty() is the opposite of (boolean) var, except that no warning is generated when the variable is not set.

You can simply use !empty($vars[1]) here.

isset() tests if a variable is set and not null:

http://us.php.net/manual/en/function.isset.php

empty() can return true when the variable is set to certain values:

http://us.php.net/manual/en/function.empty.php

To demonstrate this, try the following code with $the_var unassigned, set to 0, and set to 1.

<?php

#$the_var = 0;

if (isset($the_var)) {
  echo "set";
} else {
  echo "not set";
}

echo "\n";

if (empty($the_var)) {
  echo "empty";
} else {
  echo "not empty";
}
?>