Php Basics-use of define and defined functions

Use of php basic-define and defined functions ??? Define ("TEST_ATTR", "hhhhhhh ");??? EchoTEST_ATTR ;? Define is equivalent to the constant in java to define a constant ;? Defined () function check php Basics-use of define and defined functions

??? Define ("TEST_ATTR", "hhhhhhh ");
??? Echo TEST_ATTR;

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Define is equivalent to the constant in java to define a constant;

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The defined () function checks whether a constant exists.

If a constant exists, true is returned; otherwise, false is returned.

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Define ("GREETING", "Hello world! "); EchoDefined ("GREETING ");