# PHP Include and Require

The `include` and `require` statements allow you to insert the content of one PHP file into another PHP file (before the server executes it).

---

## 1. Difference between include and require

*   `require`: Use when the file is required by the application. If the file is not found, a **fatal error** is thrown and the script stops.
*   `include`: Use when the file is not required. If the file is not found, a **warning** is shown but the script continues.

## 2. Syntax

```php
include 'filename.php';
require 'filename.php';
```

## 3. include_once and require_once
These behave like `include` and `require`, but if the file has already been included, it will not be included again. This prevents problems like redefining functions or classes.

```php
require_once 'config.php';
```

## 4. Use Cases
*   **Headers and Footers:** Create a standard header/footer and include it on every page.
*   **Configuration:** Store database settings in a separate file.
*   **Functions:** Keep common functions in a library file.

[[programming/php/php]]