A complete list of methods to get random numbers and letters in PHP_PHP Tutorial

first method

$FileID=date("Ymd-His") . '-' . rand(100,999);

//$FileID is a random number like 20100903-132121-908

?>

The second method

function randomkeys($length) {

$returnStr='';

$pattern = '1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLOMNOPQRSTUVWXYZ';

for($i = 0; $i

$returnStr .= $pattern {mt_rand (0, 61)}; //Generate PHP random numbers

}

return $returnStr;

}

echo randomkeys(4);

?>

The third method

//seed user-defined function uses microseconds as the seed

function seed()

{

list($msec, $sec) = explode(' ', microtime());

return (float) $sec;

}

//Sow the random number generator seed and use the srand function to call the return result of the seed function

srand(seed());

//Output the generated random number, the range of random number is 10-100

echo rand(10,100);

?>

Isn’t the above one different from the one below? They both randomly output numbers between 10-100. For newbies, the question may be too simple haha

echo rand(10,100);

?>

mt_rand(10,100);

srand is the seed, if not set, the default is 1

rand is generally a fixed operation using seeds as parameters

You will know after you try it. Run rand

without setting a seed or setting a fixed seed.

Then close the browser and reopen it, then run rand

You will find that the result is always the same

Let’s talk about the rand() function first, rand([int min], [int max]) This function takes a random number between min and max. If the maximum and minimum range of random numbers are not specified, this function will automatically pick a random number from 0 to RAND_MAX.

But if you only use the rand() function, the random number will be very disordered. It is best to use the srand() function every time before taking the random number to configure a new random number seed.

Explain the following usage (this is how these two functions are generally used):

srand((double)microtime()*1000000);

$rand_number= rand();

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

Microtime() is the number of milliseconds in seconds, so the values ​​are all decimals. Multiply by 1000000 to convert them to integers

Their workflow is as follows:

(1): First, provide a "seed" to srand();, which is a value of type unsigned_int.

(2):_Then, call rand(), which will return a random number (range between _0~32767) based on the value provided to srand()

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

(4): A new "seed" can be provided to srand() at any time, thereby further "randomizing" rand()'s

Output results.

http://www.bkjia.com/PHPjc/477855.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/477855.htmlTechArticleThe first method?php $FileID=date(Ymd-His) . - . rand(100,999); / /$FileID is a random number like 20100903-132121-908? The second method?php function randomkeys($length) { $returnS...