What are common issues that can arise when using require_once in PHP?

One common issue that can arise when using require_once in PHP is that if the file being included contains a function or class that has already been declared in another file, it can cause a "cannot redeclare" fatal error. To solve this issue, you can use the function_exists() or class_exists() functions to check if the function or class has already been declared before including the file. 

if (!function_exists('myFunction')) {
    require_once 'myFile.php';
}

Keywords

require_once PHP include file path fatal error

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