PHP Random number Code _php tutorial

PHP Random number code

Today, a friend to inquire about the fire PHP random number of questions, this is the basic problem of PHP, we can refer to the fire provided PHP manual, because of time, small series also lazy writing, in the Internet to find some examples, integrated together, I hope to help you, if there are problems please say below.

　　

Seed user-defined functions with microseconds as seeds

function seed ()

{

List ($msec, $sec) = explode (' ', Microtime ());

return (float) $sec;

}

Seeding the random number generator and invoking the return result of the seed function with the Srand function

Srand (Seed ());

The output generates random numbers, and the range of random numbers is 10-100.

echo rand (10,100);

?>

Isn't this the same as the one below? are random output 10-100 between the number of new students learning, may ask too simple OH

　　

echo rand (10,100);

?>

Mt_rand (10,100);

Srand is a seed, if not set, the default is 1.

Rand is generally a fixed operation that uses seed to make parameters.

You'll find out if you try. Run Rand without seeding or setting a fixed seed

Then close the browser and open it again, and then run Rand.

You'll find the results are always the same.

But if a random number is used to seed, then the result of each run is approximate to the random

First say the rand () function, rand ([int min], [int max]) This function takes a random number between Min and Max. Without specifying the maximum and minimum range of random numbers, this function automatically takes a random number from 0 to Rand_max.

However, if only rand () is used, the random number is very chaotic and it is best to use the Srand () function to configure a new random number seed each time before taking a random number.

Explain the following usage (which is generally the case with these two functions):

Srand (Double) microtime () *1000000);

$rand _number= rand ();

Microtime () returns two values: the current millisecond and timestamp, we want to extract the random number, only a random number from the millisecond, (double) microtime () only returns the current millisecond value.

Microtime () is the number of milliseconds in seconds, and therefore the value is a decimal, multiplied by 1000000 to convert it to an integer.

; their workflow is as follows:

(1): First, give Srand () a "seed"; it is a value of type Unsigned_int.

(2): _ Then, call Rand (), which returns a random number (range between _0~32767) based on the value provided to Srand ()

(3): Call rand () as many times as needed, and get new random numbers continuously.

(4): Whenever you can provide a new "seed" for Srand (), further "Randomize" rand ()

Output results.

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