What is the difference between a generator and an array?

Question

Today the PHP team released the PHP 5.5.0 version, which includes support for generators. Reading the documentation, I noticed that it does exactly what it coul

Answer 1

An array has to contain each value that you're looping over before you start looping; a generator creates each value "on the fly" as it is requested, so a lot less memory;

An array works with the values it contains, and has to be prepopulated with those values; a generator can create values according to special criteria to be used directly... e.g. a fibonnaci sequence, or letters from a non-A-Z alphabet (calculated by the UTF-8 numeric value) effectively allowing alphaRange('א','ת');

EDIT

function fibonacci($count) {
    $prev = 0;
    $current = 1;

    for ($i = 0; $i < $count; ++$i) {
        yield $prev;
        $next = $prev + $current;
        $prev = $current;
        $current = $next;
    }
}

foreach (fibonacci(48) as $i => $value) {
    echo $i , ' -> ' , $value, PHP_EOL;
}

EDIT

Just for fun, here's a generator that will return the Hebrew alphabet as UTF-8 characters

function hebrewAlphabet() {
    $utf8firstCharacter = 1488;
    $utf8lastCharacter = 1514;
    for ($character = $utf8firstCharacter; $character <= $utf8lastCharacter; ++$character) {
        yield html_entity_decode('&#'.$character.';', ENT_NOQUOTES, 'UTF-8');
    };
}

foreach(hebrewAlphabet() as $character) {
    echo $character, ' ';
}