What does the percent sign mean in PHP?

Question

What exactly does this mean?

$number = ( 3 - 2 + 7 ) % 7;

Answer 1

It is the modulus operator:

$a % $b = Remainder of $a divided by $b.

It is often used to get "one element every N elements". For instance, to only get one element each three elements:

for ($i=0 ; $i<10 ; $i++) {
    if ($i % 3 === 0) {
        echo $i . '
';
    }
}

Which gets this output:

0
3
6
9

(Yeah, OK, $i+=3 would have done the trick; but this was just a demo.)