How can differences in PHP versions, like PHP 4 vs. PHP 5, impact the functionality of OOP programs?

Differences in PHP versions can impact the functionality of OOP programs due to changes in syntax, features, and compatibility with newer language constructs. To ensure compatibility across different PHP versions, it's important to use version-specific checks and fallbacks for unsupported features. 

// Check if a class exists before using it
if (class_exists('ClassName')) {
    $object = new ClassName();
    // Use the object as needed
} else {
    // Fallback code for older PHP versions
}

Keywords

PHP 4 PHP 5 OOP backward compatibility error handling

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