How can developers ensure their PHP code remains compatible with older versions, like PHP 4.0.6?

Developers can ensure their PHP code remains compatible with older versions like PHP 4.0.6 by avoiding the use of deprecated functions, features, and syntax that are not supported in older versions. They can also use conditional checks to detect the PHP version and adjust the code accordingly. 

if (version_compare(PHP_VERSION, '4.0.6', '<')) {
    // Code that is compatible with PHP 4.0.6
} else {
    // Code that is compatible with newer PHP versions
}

Keywords

PHP compatibility backward compatibility version control deprecated functions code refactoring

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