Why Does My PHP Code Throw a 'Fatal error: Constant expression contains invalid operations'?

Unveiling the Enigma: "Fatal error: Constant expression contains invalid operations" in PHP

Encountering the error message "Fatal error: Constant expression contains invalid operations" can be perplexing, especially when you're unsure of the exact source of the problem. To shed light on this issue, let's delve into the specific context of your code.

In the provided snippet, the error occurs in line 214 of the config.php file, where you attempt to initialize a protected static property ($dbname) based on a variable ($appdata['id']). However, as per the official PHP documentation, static properties cannot be initialized with variables under PHP versions prior to 5.6.

The reason behind this restriction is that static declarations are resolved at compile time, a stage when the content of variables is unknown. Therefore, PHP restricts static variable initialization to literals or constants to ensure that their values are known during compilation.

To resolve this issue, there are two viable options:

1. **Replace $appdata['id'] with a constant string:** This approach assigns a fixed value to $dbname, making it eligible for compile-time resolution.
2. Remove the static attribute: If the dynamic nature of $dbname is essential for your application, you can dispense with the static attribute, which will allow it to be initialized with a variable during runtime.

By addressing these issues and adhering to PHP's guidelines for static variable initialization, you can effectively eliminate this error message and ensure the smooth execution of your code.

The above is the detailed content of Why Does My PHP Code Throw a 'Fatal error: Constant expression contains invalid operations'?. For more information, please follow other related articles on the PHP Chinese website!