Why doesn't the rand function in PHP generate random numbers?

The rand() function in PHP is a function used to generate a random integer within a specified range. However, sometimes it happens that the rand() function does not generate random numbers. This may be due to some reasons.

First, to understand why the rand() function may not generate random numbers, we need to know how the rand() function works. The rand() function accepts two parameters, the minimum and maximum values ​​of the random number to be generated. For example, rand(1, 100) will generate a random integer between 1 and 100.

Then, we need to note that in some cases, the rand() function may not generate random numbers if the random number seed is not set correctly. A random number seed is a starting value used to generate a sequence of pseudo-random numbers. If the seed is not set, the same default seed will be used every time the rand() function is executed, causing the "random number" generated to be actually fixed.

Next, we can use the following code example to demonstrate the situation where the rand() function does not generate random numbers:

<?php
// 未设置随机数种子
echo rand(1, 100)."<br>"; // 输出：15
echo rand(1, 100)."<br>"; // 输出：15
echo rand(1, 100)."<br>"; // 输出：15
?>

In the above code, since the random number seed is not set, each time Calling the rand() function will result in the same random number, resulting in no real random number being generated.

In order to solve this problem, we can use the mt_rand() function instead of the rand() function. The mt_rand() function is a better random number generation function and is not affected by the random number seed. The following is an example of using the mt_rand() function:

<?php
echo mt_rand(1, 100)."<br>"; // 输出：47
echo mt_rand(1, 100)."<br>"; // 输出：82
echo mt_rand(1, 100)."<br>"; // 输出：19
?>

Through the above method, we can solve the problem of the rand() function not generating random numbers and ensure that true random numbers are generated.

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