rand()

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rand()

rand() returns a pseudo-random number between 0 and 1. No argument is required.

Getting 1-based ranges vs. zero-based ranges of values

Consider:

$MyNumber=round(rand()*10); 

$MyNumber will be set to one of eleven integers in the range 0 through to 10.

But, what if the '10' argument about is actually a child count:

$MyNumber=round(rand()*$ChildCount); 

If the $ChildCount was 10 and $MyNumber were used to fetch a random child using $SiblingOrder($MyNum) the process would fail if $MyNumber were zero. $SiblingOrder numbers from 1. Indeed, in this case the need is for ten integers, one through to ten.

A 1-based range can be achieved:

$MyNumber=round(rand()*(10-1))+1; 

$MyNumber=round(rand()*($ChildCount-1))+1; 

If the main input is 10, by subtracting 1 the process returns a randomised integer in in the range 0-9 (ten numbers) and then adding back 1 shifts the value range to 1-10.