php random number code_PHP tutorial

php random number code

Today, a friend asked Agni about PHP random numbers. This is a basic question of PHP. You can refer to the PHP manual provided by Agni. Due to time Regarding the relationship, the editor is too lazy to write. I found some examples on the Internet and put them together. I hope it will be helpful to everyone. If you have any questions, please tell me below.

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

Function seed()

　{

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

return (float) $sec;

　}

// Sow the seed of the random number generator 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 and 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

But if you use a random number as a seed, the result of each run will be approximately random

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 chaotic. It is best to use the srand() function to configure a new random number seed before taking the random number each time.

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): You can provide a new "seed" to srand() at any time to further "randomize" rand()'s

Output the results.

http://www.bkjia.com/PHPjc/848324.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/848324.htmlTechArticlephp random number code Today, a friend asked about the problem of Agni PHP random number. This is a basic problem of PHP. Everyone You can refer to the PHP manual provided by Agni. Due to time constraints, the editor...