How can the use of include_once and require_once prevent the redeclaration of functions in PHP?

When including files in PHP using `include` or `require`, functions and classes defined in those files are loaded into the current script. If the same file is included multiple times, it can lead to redeclaration errors for functions or classes. To prevent this issue, we can use `include_once` or `require_once` instead, which will only include the file if it has not been included before, thus avoiding redeclaration errors. 

// Using include_once to prevent redeclaration of functions
include_once 'my_functions.php';
```

```php
// Using require_once to prevent redeclaration of functions
require_once 'my_functions.php';

Keywords

include_once require_once redeclaration functions PHP

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