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Understanding include(), require(), include_once(), and require_once() in PHP

When developing in PHP, it's essential to understand the differences between include(), require(), include_once(), and require_once() functions. These functions are used to include external files into your PHP code, but they differ in their behavior:

The Difference:

• include(): The include() function includes and evaluates a specified file during script execution. If the file is not found, a warning is issued, but the script continues.
• require(): The require() function is similar to include(), but if the specified file is not found, a fatal error occurs, and script execution stops.
• include_once(): This function behaves like include(), but ensures that the file is included only once in a particular script, preventing multiple inclusions.
• require_once(): Similarly to require(), require_once() includes a specified file, but ensures that the file is included only once in a script to avoid duplication.

Using these functions correctly based on your needs can enhance code management and prevent errors in PHP applications.

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