获得的价值不会太接近最后的价值

I'm trying to create a function that will echo a new value between 1 and 6, but it can't be within + or - 1 of the last time the function was run. (i.e. If the last time it ran it got 4, I need a new value between 1 and 6 that's not 3, 4, or 5.)

As a php noob here's what I have so far:

    $prev_val = 8;
    function wordsize () {
        global $prev_val;
        $size_array = range(1,6);
        do {
            $new_val = $size_array[array_rand($size_array)];
        } while($new_val>$prev_val-1 && $new_val<$prev_val+1);
        echo "$new_val";
        $prev_val = $new_val;
    }

$size_array = array_diff(range(1,6), range($prev_val - 1, $prev_val + 1));

Which removes the need for a while entirely.

You almost got it, you need to use >= and <= in your while loop:

while($new_val>=$prev_val-1 && $new_val<=$prev_val+1);

However, it might be better to get rid of the while loop entirely. See @wrikken's answer.