Comparative introduction to empty function and isset function in php

This article brings you a comparative introduction to the empty function and isset function in PHP. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

A common topic, the reason why these two functions are used for comparison is because they are often used to determine whether a variable is empty, but they are somewhat different. Let’s compare them below.

Definition

Let’s first look at the manuals of the two functions

empty

empty — Check whether a variable is empty

bool empty (mixed $var)

Determine whether a variable is considered empty. When a variable does not exist, or its value is equal to FALSE, then it is considered not to exist. empty() does not generate a warning if the variable does not exist.

isset

isset — Check whether a variable has been set and is not NULL

bool isset ( mixed $var , [mixed $... ] )

Check whether the variable is set and not NULL.

It can be seen from the manual that the focus of the two functions is whether the focus of empty is empty and whether the focus of isset is set and non-NULL.

Comparison

The following lists several possible null values. Use two functions to determine whether the variable is empty, and compare whether the return value meets expectations (Note: isset returns false is equivalent to empty returns true).

##0bool(true)bool(true) Not the same##array()UndefinedConclusion

Variable value	empty	isset	Is it the same
false	bool(true)	bool(true)	Not the same
null	bool(true)	bool(false)	Same
''	bool(true)	bool(true)	Not the same
'0'	bool(true)	bool (true)	Not the same
bool(true)	bool(true)	Not the same
bool(true)	bool(false)	Same

As can be seen from the above table, empty considers all values ​​​​to be empty; while isset, except null and undefined, considers it to be set and non-NULL. After understanding the differences between the two functions, you can choose according to your needs when writing code.

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