PHP中的聲明（strict_types = 1）指令是什麼

答案：declare(strict_types=1)啟用後，PHP函數參數將強制類型檢查，禁止自動類型轉換。例如，期望int時傳入string會拋出TypeError而非嘗試轉換。該聲明必須位於文件首行，僅作用於當前文件的用戶函數參數，不直接影響返回類型或內部函數。配合返回類型聲明可提升代碼可靠性與可維護性。

The declare(strict_types=1) directive in PHP enables strict type checking for function arguments in the current file. By default, PHP uses loose typing, meaning it automatically converts values to the expected type when possible. With strict types enabled, PHP will only accept values of the correct type and will throw a TypeError if there's a mismatch.

How It Works

When you add declare(strict_types=1); at the top of a PHP file, it affects how function calls are handled in terms of type compatibility. This declaration only applies to the file it's declared in.

• Type declarations (like int, string, array, etc.) are enforced strictly.
• No automatic type conversion is performed for scalar types.
• If a function expects an integer and you pass a string, PHP throws a TypeError instead of trying to convert it.

Example: Strict vs Loose Types

Without strict_types=1 , this would work because PHP would convert the strings to integers. With strict types, it fails.

Important Notes

• The directive must be the very first statement in the script or after the opening
• It only affects function arguments in user-defined functions, not return types (those have their own strict setting).
• It does not affect internal PHP functions — they still behave as usual.
• To enable strict checking for return types, use declare(strict_types=1) along with return type declarations.

Using declare(strict_types=1) helps catch bugs early by ensuring data types are used consistently, making your code more predictable and easier to debug.

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