$a = filter_input(INPUT_GET, 'a'); // "foo" $b = filter_input(INPUT_GET, 'b'); // false $c = filter_input(INPUT_GET, 'c'); // null $a = (string)filter_input(INPUT_GET, 'a'); // "foo" $b = (string)filter_input(INPUT_GET, 'b'); // "" $c = (string)filter_input(INPUT_GET, 'c'); // "" /* 1. 未定義や想定外の型の検出 */ $email = (string)filter_input(INPUT_POST, 'email'); /* 2. 値の形式に関するバリデーション */ if (false !== filter
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