生成随机数字和字母

// A string with random letters and numbers. A-Z, a-z, 0-9


// A function in PHP is a block of code that can be used elsewhere in code.
// This function is called rand_string and will generate a random sequence of characters in one string.
// A default value of 16 characters is set, so that if no integer is supplied it will use the value of 16.
function rand_string($length = 16) {

    // A string is something that holds alphanumeric characters and other symbols. 
    // This string is an empty one, or at least that's how it starts.
    $string = '';

    // This is known as a for/next loop, it's will run a section of code for a set number of times.
    // A counter $i is incremented on each pass. In this case until it has operated $length number of times.
    for ($i = 0; $i < $length; $i++) {

        // This variable ($die) is assigned a random number - which is obtained via the PHP function mt_rand.
        //Consult the PHP docs for more information.
        $die = mt_rand(1, 3);

        // This switch statement picks a case that is true and runs the accompanying code as defined in each case.
        switch ($die) {

            // This case will be activated if the variable $die has the value of 1. And case 2 if it has the value of 2 and so on.
            case 1:
                // Here and subsequently a random value between 48 and 57 is assigned to the $rnd variable.
                $rnd = mt_rand(48, 57);
                break;

            case 2:
                $rnd = mt_rand(65, 90);
                break;

            case 3:
                $rnd = mt_rand(97, 122);
                break;
        }

        // This is another variable $string which is assigned the ASCII character that is represented by the $rnd variable.
        // ASCII characters are codes that computers use to represent characters and symbols.
        // The chr function is a special PHP function that returns the character represented by the ASCII code.
        // In this case the value of $rnd.
        $string .= chr($rnd);
    }

    // Here we reach the final result. The value of $string is returned to source of the function call.
    return $string;
}

// Segments of the function, loops and switches are enclosed between curly brackets {}. This limits the scope of the processing contained within.

// Usage of this function to obtain a 10 character random string.
// echo is a function that prints the result to the browser/screen.
$mystring = rand_string(10);
echo $mystring;

最简单的方法是完全掌控：

<?php
$str = 'QaR0SbT1UcV2WdX3YeZ4f5g6h7i8j9kAlBmCnDoEpFqGrHsItJuKvLwMxNyOzP';
// a-z 0-9 A-Z in above string

$shuffled = str_shuffle($str);

$shuffled = substr($shuffled,1,30);

echo $shuffled;
?>

根据您的需求更改 $str。我使用了小写字母 a 到 z，大写字母 A 到 Z 和数字值 0 到 9。

我编写了一个用于生成随机数和字符串的PHP类PHPRandomValue。

它使用“mcrypt_create_iv(4, MCRYPT_DEV_URANDOM)”生成随机数和值。我是在开发加密项目时制作的，因为我需要一个安全的随机值生成器，而mt_rand()无法满足此要求。以下是一个示例用法：

$randomValue = new RandomValue;

$randomValue->randomNumber(): = -3880998

$randomValue->randomNumberBetween(1,10): = 2

$randomValue->randomTextString(): = CfCkKDHRgUULdGWcSqP4

$randomValue->randomTextString(10):  = LorPIxaeEY

$randomValue->randomKey(): = C7al8tX9.gqYLf2ImVt/!$NOY79T5sNCT/6Q.$!.6Gf/Q5zpa3

$randomValue->randomKey(10):  = RDV.dc6Ai/

这将基于变量字符创建随机的字母数字字符串：

function createRandomCode() 
{     
    $chars = "abcdefghijkmnopqrstuvwxyz023456789";     
    srand((double) microtime() * 1000000);     

    $i = 0;     
    $pass = '';  

    while ($i <= 7) 
    {         
        $num = rand() % 33;         
        $tmp = substr($chars, $num, 1);         
        $pass = $pass . $tmp;         
        $i++;     
    }    

    return $pass; 
}