Detailed explanation of the steps to generate a random string of custom length in PHP

This time I will bring you a detailed explanation of the steps to generate a random string with a custom length in php. What are the precautions for generating a random string with a custom length in php? The following is a practical case. , let’s take a look.

//随机生成字符串
function random($length) {
     srand(date("s"));
     $possible_charactors = "0123456789abcdefghijklmnopqrstuvwxyz";
     $string = "";
     while(strlen($string)Example 2, php generates n non-repeating random number instances<p style="text-align: left;">Use php to generate n non-repeating random number instances<br></p>There are 25 works for voting. You need to select 16 works in one vote, and a single work can only be selected once in one vote. <p style="text-align: left;">A programmer made a mistake earlier and forgot to store the votes in the database. The voting sequences generated by 200 users were empty. So how do you fill this gap? <br>Need to generate 16 non-repeating random numbers between 1-25 to fill. How to design the function specifically? Store random numbers in an array, and then remove duplicate values ​​in the array to generate a certain number of non-repeating random numbers. <br>Program:<br></p><pre class="brush:php;toolbar:false"><?php /*
* array unique_rand( int $min, int $max, int $num )
* 生成一定数量的不重复随机数
* $min 和 $max: 指定随机数的范围
* $num: 指定生成数量
*/ www.jbxue.com
function unique_rand($min, $max, $num) {
    $count = 0;
    $return = array();
    while ($count < $num) {
        $return[] = mt_rand($min, $max);
        $return = array_flip(array_flip($return));
        $count = count($return);
    }
    shuffle($return);
    return $return;
}
$arr = unique_rand(1, 25, 16);
sort($arr);
$result = &#39;&#39;;
for($i=0; $i < count($arr);$i++)
{
 $result .= $arr[$i].&#39;,&#39;;
}
$result = substr($result, 0, -1);
echo $result;
?>

Program running:

2,3,4,6,7,8,9,10,11,12,13,16,20,21,22,24

Supplement:

The mt_rand() function is used to generate random numbers. This function generates random numbers four times faster on average than rand().
The "flip method" is used to remove duplicate values ​​in the array, which is to use array_flip() to exchange the key and value of the array twice. This approach is much faster than using
array_unique(). Before returning the array, first use shuffle() to assign new key names to the array, ensuring that the key names are consecutive numbers from 0-n. If this step is not performed, the key names may be discontinuous when
deleting duplicate values, causing trouble for traversal.

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!

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