Empty, isset, is_null comparison (1/4)

Empty, isset, and is_null functions have some problems. It even brings some security bugs to your programs. Most of the time, empty considers isset to be similar. Therefore, during development, I did not pay attention to it. When a piece of code is used as a process judgment, a bug occurs.

 I. Examples

A. a variable is not defined. How should we judge it?

 

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01

<?php

02	# Does not exist$test Variable

03

04	$isset= isset($test)?"test is define!":"test is undefine!";

05	echo "isset:$issetrn";

06

07	$empty=!empty($test)?"test is define!":"test is undefine!";

08	echo "empty:$emptyrn";

09

10	$is_null=is_null($test)?"test is define!":"test is undefine!";

11	echo "is_null:$is_nullrn";

 

The test result is:

The result is: empty and isset first checks whether the variable exists and then checks the variable value. Is_null only checks the variable value directly and determines whether it is null. Therefore, if the variable is undefined, an error occurs!

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