A brief discussion on the difference between isset() and empty() functions in PHP

It is easy to confuse between isset() and empty() in PHP. They are both used to test the value of variables and both return a Boolean value. The following article will take you to understand isset() and empty(), I hope it will be helpful to you.

PHP isset() function

isset() function is used to determine whether a variable has been set and is not null; in other words, returns true only if the variable is not null.

Basic sentence structure:

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

Example:

<?php
header("content-type:text/html;charset=utf-8");  
function checkIfIsset($value)
{
if(isset($value)) {
return "它被设定";
}else {
return "它没被设定";
}
}
 $value = false;  
 echo checkIfIsset($value);  
?>

Output:

PHP empty() function

empty() function is used to determine whether a variable is empty; in other words, if the variable is an empty string, false, array(), NULL, "0 ”, 0 and unset variables, it will return true.

Basic sentence pattern:

bool empty(mixed var)

Example:

<?php
header("content-type:text/html;charset=utf-8");  
 function checkIfnotEmpty($value){  
      if (!empty($value)) {  
        return "它不是空的";  
      } else {  
        return "它是空的";  
      }  
 } 
 $value = &#39;&#39;;  
 echo checkIfnotEmpty($value);  
?>

Output:

The difference between isset() and empty() functions in PHP

1. If the isset() function contains flase, 0 or empty string value, it will return true; otherwise it will return false. The empty() function returns true if it contains empty, 0, null or false values; if the string contains non-empty and non-zero values, it returns false.

2. If the value does not exist, the isset() function will return false, and the empty() function will return true.

The following table is a simple reference of what these functions will return for the different values. A space indicates that the function returns bool (false).

##array() (an empty array) Boolean (true) Boolean (true)##NUll value"0"(0 as string) 0 (0 is an integer) 0.0 (0 as Floating point number) var $ var;

Value of variable ($var)	isset($var)	empty($var)
""(empty character String)	Boolean (true)	Boolean (true)
“ “ (space character)	Boolean (true)
##false	## Boolean (true)	Boolean (true)
true	Boolean (true)
	Boolean (true)
Boolean (true)	Boolean (true)
Boolean (true)	Boolean (true)
Boolean (true)	Boolean (true)
(Declared variable, but no Value)	##Boolean (true)
NUllbyte("\0")Boolean (true)		The above is the entire content of this article, I hope it will be helpful to everyone's study. For more exciting content, you can pay attention to the relevant tutorial columns of the PHP Chinese website! ! !

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