php rand() random function generates random number code

First, let’s get to know the random number function rand() provided by php. The rand() function of php will return a random integer. The specific usage method is as follows:

rand(min,max)

The optional parameters min and max can make rand () Returns a pseudo-random integer between 0 and rand_max. For example, if you want a random number between 5 and 15 (including 5 and 15), use rand(5, 15).

Let me look at a specific example below , we make a basic function call without setting specific parameters. The random number we get will not be limited by the min and max parameters. The code is as follows:

echo(rand());?>

The result obtained: 652696728 (random result) 1. Use php to generate random numbers within the specified interval. If we want to generate a random number between two numbers, we need to set two parameters for rand: In this way, we get The result is under our control, it should be minnum

echo(rand( 1000,2000));?>

It’s simple enough, let’s do something a little more difficult. At the beginning of this article, we said that random numbers are very useful. We can use PHP random numbers to solve some complex problems. 2. Use PHP to obtain a random element in a collection. Suppose we need to obtain a random element from an array. The code is as follows:

$my_array=array('asp','php','webpage','ajax', 'css','jquery','html');

echo($my_array[rand(0,6)]);

It is conceivable that the result we get may be any one of asp, php or javascript contained in Elements in the array. Note that our my_array array contains seven elements. We set the parameters of rand() to between 0 and 6. Next, we use two sets of random numbers to enhance the function of the above example. We need a random number to perform conditional judgment, and another random number to output the element. The code is as follows:

$my_array=array('asp','php','javascript','ajax','css','jquery','html ');

$repetition=rand(0,6);

for($i=0;$i

echo('i am learning ' . $my_array[rand( 0,6)]);

echo(' on 51cto.com');

}

The results we get may look like the following:

The first time we run we get three results, because we use a random number Limit the number of displayed items, so in addition to random articles, the results obtained are also random.

The second run got seven results

Maybe you will ask, can PHP random numbers only do these boring things? ?rand() does not seem to be that important; you are wrong, think about the verification codes that can be seen everywhere, the random article extraction of some CMS systems, download address allocation, etc. Random numbers play an important role in these applications. In addition, in In the field of security and algorithms, many applications of random numbers are also worthy of our in-depth study, such as encryption and congruence structure. The code is as follows:

$ip2id= round(rand(600000, 2550000) / 10000) ; //The first method, directly generate

$ip3id= round(rand(600000, 2550000) / 10000);

$ip4id= round(rand(600000, 2550000) / 10000);

//The following is The second method is to randomly select from the following data

$arr_1 = array("218","218","66","66","218","218","60","60", "202","204","66","66","66","59","61","60","222","221","66","59","60 ","60","66","218","218","62","63","64","66","66","122","211");

$ randarr= mt_rand(0,count($arr_1)-1);

$ip1id = $arr_1[$randarr];

echo $ip1id;

echo ".";

echo $ip2id;

echo " .";

echo $ip3id;

echo ".";

echo $ip4id;

?>