When is the constant of PHP released?

Title, in the project set a judge, the constant value does not exist jump to a page and assign a value to the constant. But except for the first jump, after I closed the browser again after I still can't jump, ask PHP's constant release mechanism

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Title, in the project set a judge, the constant value does not exist jump to a page and assign a value to the constant. But except for the first jump, after I closed the browser again after I still can't jump, ask PHP's constant release mechanism

Variables and constants generated by a request are freed at the end of the request

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