php empty() error, Fatal error: Can’t use function return_PHP tutorial

Today when I was using the empty function, I got a Fatal error: Can't use function return value in write context error message. I thought it was very strange. I have been using this function for a long time. What happened today? Let's take a look at it. analysis process.

Error message

Fatal error: Can’t use function return value in write context in empty.php on line 5

My code is written like this

It can be seen that empty can only be used to check variable values ​​and cannot be used to check the return value of a function. The correct usage should be

The code is as follows

代码如下	复制代码
$str=” “; if(empty(trim($str))){ echo “empty”; }

Copy code

$str=” “;
if(empty(trim($str))){
echo “empty”;
}

Then it appeared

Fatal error: Can’t use function return value in write context in empty.php on line 5

I couldn’t see the reason so I went to the official website and checked the manual.

bool empty ( mixed $var )

代码如下	复制代码
$var =trim(” “); // 结果为 true，因为 $var 为空字符串 if (empty($var)) { echo ‘empty’; }

If var is a non-empty or non-zero value, empty() returns FALSE. In other words, "", 0, "0", NULL, FALSE, array(), var $var; and objects without any properties will be considered empty, and TRUE will be returned if var is empty. empty() is the antonym of (boolean) var, except that it does not produce a warning when the variable is not set.

The code is as follows

Copy code

$var =trim(” “); // The result is true because $var is an empty string if (empty($var)) { echo ‘empty’; } The usage of empty(trim($str) is wrong. http://www.bkjia.com/PHPjc/632096.html www.bkjia.comtruehttp: //www.bkjia.com/PHPjc/632096.htmlTechArticleToday when using the empty function, a Fatal error: Can't use function return value in write context error message appeared, I think It's strange. I have been using this function for N long. What happened today...