Quick example in elegance using PHP and Ruby. PHP forces us to use the bang to check for not. Ruby has `unless` which allows, in my opinion, a more fluid way to write code.

array.php

<?php

$my_array = array('apple', 'pear', 'cherry')

// If I want to find out if a value is in an array with PHP I do this:

if (in_array('apple', $my_array)) {
  echo 'Apple is in the array!';    // => Apple is in the array!
}

// If I want to check if there isn't a variable in an array:

if (!(in_array('earthworm', $my_array))) {
  echo 'Earthworm is not in the array!';    // => Earthworm is not in the array!
}

array.rb

my_array = %w[apple pear cherry]

# In Ruby I can do this to see if something is in an array:

if my_array.include?('apple') do
  puts 'Apple is in the array!' # => Apple is in the array!
end

# If I'm checking if something isn't in an array:

unless my_array.include?('earthworm') do
  puts 'Earthworm is not in the array!' # => Earthworm is not in the array!
end

Something to note: I didn't do the in-line puts with the Ruby example to try and show the Ruby example more like the PHP one.

Here's another perfectly valid way of writing the Ruby example:

my_array = %w[apple pear cherry]

puts 'Apple is in the array!' if my_array.include?('apple')

puts 'Earthworm is not in the array!' unless my_array.include?('earthworm')