- printf: documentation ( source)
<?php
printf("2 ** 3 == %d\n", 2 ** 3);
printf("3 ** 4 == %d\n", 3 ** 4);
printf("2 ** 3 ** 4 == %d\n", 2 ** 3 ** 4);
printf("(2 ** 3) ** 4 == %d\n", (2 ** 3) ** 4);
printf("2 ** (3 ** 4) == %d\n", 2 ** (3 ** 4));
$a = 2;
$a **= 3;
printf("a == %d\n", $a);