Differences between empty, isset, and is_null in PHP

Introduction: This is a detailed page on the differences between empty, isset, and is_null in PHP. It introduces empty, isset, is_null, PHP, differences between empty, isset, and is_null in PHP are related knowledge, skills, experience, and some PHP source code.

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Empty

If the variable is not null or a non-zero value, empty () returns false. In other words, "", 0, "0", null, false, array (), VAR $ var, undefined, and objects without any attributes will be considered empty, if VaR is null, true is returned.

Isset

If the variable exists (not null), true is returned; otherwise, false (including undefined) is returned ). If the value of a variable is set to null, false is returned. If a variable is unset, the variable is canceled. Note that isset has special processing for null variables.

Is_null

Checks whether the input value [value, variable, expression] is null. Only if one variable is defined and its value is null, true is returned. otherwise, false is returned. [an error will occur after an undefined variable is passed in! ].

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