Trouble when generating an array of random values

Question

I'm generating an array of random numbers, between 0 and 2 with this code:

    for ($j = 0; $j < 60; $j++) {
       for ($i = 0; $i < 100; $i++) {
                $value = rand(0,2);
                $DBH->query("INSERT INTO map (x, y, value) VALUES($i, $j, $value);");
    }

And i found and oddity, as you may see here, the rows are random, but they repeat:

22121000210211220022122200120200122000122121
22121000210211220022122200120200122000122121
22121000210211220022122200120200122000122121
22121000210211220022122200120200122000122121
22121000210211220022122200120200122000122121

How can avoid that?

El Yobo · Accepted Answer · 2010-12-06 02:59:33Z

3

You might want to explicitly seed your generator using srand, e.g. srand(time()) (note that the srand link has a better example of seeding than just using time, depends on how random you need, I suppose).

Failing that

You could try using mt_rand with mt_srand
You could always use MySQL's rand function to generate the numbers as a workaround.

answered Dec 6, 2010 at 2:59

El Yobo

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1 Comment

Jere Over a year ago

Just saw this interesting comparison on mt_rand: portfolio.technoized.com/notes/26

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