The difference between isset, empty and is_null

isset(): Only when null and undefined, return true

empty(): "", 0, "0", NULL, FALSE, array(), undefined, all return true

is_null(): Only determine whether it is null, and a warning will be reported if it is not defined

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The above has introduced the differences between isset, empty and is_null, including the relevant aspects. I hope it will be helpful to friends who are interested in PHP tutorials.