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I have this:
<?php $n = rand(1,1600); echo $n ?>
I want to exclude from random numbers let's say 234, 1578 ,763 , 1274 and other numbers. How would I do that?
877
By default, rand returns normalized values (between 0 and 1) that are drawn from a uniform distribution. To change the range of the distribution to a new range, (a, b), multiply each value by the width of the new range, (b – a) and then shift every value by a.
rand() or mt_rand() functions can be used to Generate 5 Digit Random Number in PHP.
The rand() function generates a random integer. Example tip: If you want a random integer between 10 and 100 (inclusive), use rand (10,100). Tip: As of PHP 7.1, the rand() function has been an alias of the mt_rand() function.
RAND returns an evenly distributed random real number greater than or equal to 0 and less than 1. A new random real number is returned every time the worksheet is calculated.
As the volume of "blacklisted" integers approaches the volume of the full range of integers, it becomes increasingly compelling to take the advice of @regenschein.
A non-iterative approach might look like this:
$range = range(1, 1600);
$blacklist = [234, 1578, 763, 1274]; // 4 blacklisted versus 1600 full range is NOT compelling
$valids = array_diff($range, $blacklist);
echo array_values($valids)[rand(0, count($valids) - 1)];
// or
echo $valids[array_rand($valids)];
// the two approaches use different randomizers
Or if you'd be just as happy shuffling, you could do:
$blacklist = [234, 1578, 763, 1274];
$range = range(1, 1600);
$valids = array_diff($range, $blacklist);
shuffle($valids);
echo $valids[0];
*Note array_diff() is particularly great if you want to pass multiple blacklist arrays -- just comma-separate them.
For example:
var_export($valids = array_diff(range(1, 100), range(5, 50), range(61, 99), [55]));
Output:
array (
0 => 1,
1 => 2,
2 => 3,
3 => 4,
50 => 51,
51 => 52,
52 => 53,
53 => 54,
55 => 56,
56 => 57,
57 => 58,
58 => 59,
59 => 60,
99 => 100,
)
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