PHP: isset - Manual

Getting Started Introduction A simple tutorial Language Reference Basic syntax Types Variables Constants Expressions Operators Control Structures Functions Classes and Objects Namespaces Enumerations Errors Exceptions Fibers Generators Attributes References Explained Predefined Variables Predefined Exceptions Predefined Interfaces and Classes Predefined Attributes Context options and parameters Su

[himabato]

変数が宣言されているかどうかを調べてくれる

[takaken1123]

[2015-09-16 12:59]

[a20130517]

NULLのときはfalse返してくれる。“返り値 ¶ var が存在して NULL 以外の値をとれば TRUE、 そうでなければ FALSE を返します。”

[omoon]

be careful! using isset($array['key']['subkey']) doesn't work as one could expect