Why Does PHP Throw a \'Can\'t use function return value in write context\' Error, and How Can I Fix It?

PHP Error Handling: Deciphering the "Can't use function return value in write context" Conundrum

The enigmatic error message "Fatal error: Can't use function return value in write context" can be puzzling, especially when it pertains to a line that appears relatively straightforward. To unravel this error, let's delve into the context and the code causing the issue.

The error message indicates that an attempt was made to assign a function return value to a variable within an if statement on line 48. However, in PHP, function return values cannot be used directly in a write context, such as in an assignment statement. The affected line, "if (isset($_POST('sms_code') == TRUE ) {", illustrates this mistake. Line 48 attempts to assign the result of the isset() function, which returns a boolean, to a variable.

To resolve this issue, the code can be modified to assign the result to a variable and then use that variable in the if condition. For instance, the following modification will work:

$isset_result = isset($_POST('sms_code'));
if ($isset_result == TRUE) {

Alternatively, a ternary operator can be used to simplify the code:

$state = $isset_result ? CORRECT_CODE : NOTHING_SUBMITED;

Additionally, as mentioned in the provided answer, empty() should only be used with variables and not function return values. In cases where empty() is intended to be used with function return values, the trim() function can be employed instead. For example:

!empty(trim($someText)) ? doSomething() : doSomethingElse(); 

By addressing these issues, the code will function as expected, and the "Can't use function return value in write context" error will no longer occur.

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