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Q:

PHP Error : Fatal error: Constant expression contains invalid operations

Hey everyone,

I hope you're all doing well. I'm currently facing an issue with my PHP code and I could use your expertise to help me out.

I'm getting the following error: "Fatal error: Constant expression contains invalid operations".

Here's some context on what I'm trying to achieve in my code:

I have a constant called "MY_CONSTANT" that I'm using in my PHP script. Inside a class, I'm trying to use this constant within an if statement, but it seems like I'm making some mistake.

Here's a simplified version of my code:

```php
class MyClass {
const MY_CONSTANT = 5;

public function myFunction() {
$myVariable = 10;

if ($myVariable > (self::MY_CONSTANT * 2)) {
// Some code here
}
}
}
```

The error seems to be related to the expression `(self::MY_CONSTANT * 2)`. It looks like I can't perform this multiplication operation inside the if statement.

I'm not sure why this is happening. I have used constant expressions in PHP before without any issues, but this specific scenario is giving me trouble.

I would really appreciate it if someone could shed some light on why I'm receiving this error and provide a solution to overcome it.

Thank you in advance for your help!

All Replies

max62

User 1: Hi there,

I've encountered a similar error before and I think I might have a solution for you. The error message "Constant expression contains invalid operations" usually occurs when you try to perform a non-static operation or use a non-constant value inside a constant expression.

In your case, the error is caused by using the multiplication operator (*) inside the constant expression. PHP can only evaluate constant expressions during compilation, and the result must be a simple value like a number, string, or boolean.

To overcome this error, you can try replacing the constant expression with a variable expression. Here's an updated version of your code:

php
class MyClass {
const MY_CONSTANT = 5;

public function myFunction() {
$myVariable = 10;
$constantExpression = self::MY_CONSTANT * 2;

if ($myVariable > $constantExpression) {
// Some code here
}
}
}


By moving the expression `(self::MY_CONSTANT * 2)` into a variable `$constantExpression`, you avoid the direct use of the multiplication operator inside the if statement.

Give it a try and see if it resolves your issue. Let me know if you have any further questions!

marcia94

User 2: Hey there,

I completely understand the frustration and confusion caused by this error. I faced a similar issue a while ago, and it took me some time to figure out the root cause. Let me share my experience with you.

The error message "Constant expression contains invalid operations" is mostly triggered when you use an incorrect operation within a constant expression. In your case, it seems like you're attempting to perform a mathematical operation using the multiplication operator (*) inside the constant expression.

To overcome this error, one possible solution is to use a different approach. Instead of using a constant expression, you can define a static variable inside your class and assign the result of the multiplication to it. Here's an example based on your code:

php
class MyClass {
const MY_CONSTANT = 5;
static $constantExpression;

public function myFunction() {
$myVariable = 10;

self::$constantExpression = self::MY_CONSTANT * 2;

if ($myVariable > self::$constantExpression) {
// Some code here
}
}
}


By utilizing a static variable, you can perform the multiplication operation (`self::MY_CONSTANT * 2`) during runtime and assign the result to the static variable `$constantExpression`. This way, you can avoid the restriction of constant expressions and still achieve the desired functionality.

Give this approach a try and let me know if it resolves your issue or if you need any further assistance. Best of luck!

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