How do you declare constants in PHP and what's the difference between define() and const?

beginner

Re-explain

Constants can be declared using define() function or const keyword:

define(): Can be used anywhere, supports dynamic names and conditional declaration
const: Must be declared at top-level scope, faster at compile time, supports class constants

define('MAX_SIZE', 100);
const MIN_SIZE = 10;

// define() can be conditional
if ($condition) {
    define('DYNAMIC', 'value');
}
// const cannot be used conditionally

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