By setting the documentation
echo rand() // Imprime algo completamente aleatório
echo rand($min, $max) // Imprime algo em um range entre min e max
In a code, inside a loop, I accidentally generated the following rand($max, $min) I noticed the bizarre behavior, it does not generate a warning saying that the value of the first parameter should not be greater than the value of the second, as if for example I omitted just one of the values, which would generate me:
E_WARNING: type 2 - rand () expects exactly 2 parameters, 1 given
If I use the mt_rand function, for example, it gives me the warning:
E_WARNING: type 2 - mt_rand (): max () is smaller than min ()
But with rand generated values with a peculiar behavior that made me curious
Testing for example the following code:
for($j = 0; $j < 10; $j++){
for($i = 0; $i < 10; $i++){
if($i < 9) echo rand(10,0).",";
else echo rand(10,0)." | teste -> ".($j+1)."<br/>";
}
}
I got more or less the following:
3,10,4,5,7,8,4,9,5,2 | teste -> 1
2,2,10,5,9,6,8,2,5,2 | teste -> 2
7,8,4,10,5,7,8,8,5,4 | teste -> 3
9,7,4,3,10,10,9,4,8,4 | teste -> 4
5,8,4,4,3,3,8,10,4,3 | teste -> 5
2,9,9,5,8,4,10,5,10,5 | teste -> 6
8,9,10,2,10,9,10,9,2,8 | teste -> 7
2,6,6,5,9,8,7,6,8,9 | teste -> 8
8,8,7,6,2,5,8,2,9,8 | teste -> 9
5,6,6,4,7,6,3,6,4,4 | teste -> 10
And worse! If you change rand to closest values, type rand(10,8) , it prints:
10,10,10,10,10,10,10,10,10,10 | teste -> 1
10,10,10,10,10,10,10,10,10,10 | teste -> 2
10,10,10,10,10,10,10,10,10,10 | teste -> 3
10,10,10,10,10,10,10,10,10,10 | teste -> 4
10,10,10,10,10,10,10,10,10,10 | teste -> 5
10,10,10,10,10,10,10,10,10,10 | teste -> 6
10,10,10,10,10,10,10,10,10,10 | teste -> 7
10,10,10,10,10,10,10,10,10,10 | teste -> 8
10,10,10,10,10,10,10,10,10,10 | teste -> 9
10,10,10,10,10,10,10,10,10,10 | teste -> 10
I tested the following online emulators: repl.it , ideone.com and phpfiddle.org and I noticed that in those that use more current versions of PHP this does not happen, I went deeper and found this emulator to choose old versions: sandbox.onlinephpfunctions.com and I saw that until version 7.0.14 this still happened, I tried to look for some thing in the php.net changelog and in the official php repository at gitHub but could not find anything about it.
Anyway, this is a mistake, and it should not even exist in code! But it struck me as a curiosity, which actually happens with the rand function in old versions of PHP, when a max value is less than the min value?