The rand keyword

rand is a function that returns a random fractional number greater than or equal to 0 and less than the value of EXPRESSION. Without EXPRESSION, the value 1 is used so that the interval of the random number is ${\displaystyle [0,1)}$.

  rand EXPRESSION
  rand

Examples

The code

$a = rand(31);
print 'int(' . "$a" . ') = ', int($a);

returns a number [0, 31) like

 int(28.7540893554688) = 28