以前的答案会生成不安全或难以输入的密码。

这是安全的，并且提供了用户更有可能实际使用的密码，而不是因为一些薄弱的东西而被丢弃。

// NOTE: On PHP 5.x you will need to install https://github.com/paragonie/random_compat

/**
 * Generate a password that can easily be typed by users.
 *
 * By default, this will sacrifice strength by skipping characters that can cause
 * confusion. Set $allowAmbiguous to allow these characters.
 */
static public function generatePassword($length=12, $mixedCase=true, $numericCount=2, $symbolCount=1, $allowAmbiguous=false, $allowRepeatingCharacters=false)
{
  // sanity check to prevent endless loop
  if ($numericCount + $symbolCount > $length) {
    throw new \Exception('generatePassword(): $numericCount + $symbolCount are too high');
  }

  // generate a basic password with just alphabetic characters
  $chars  = 'qwertyupasdfghjkzxcvbnm';
  if ($mixedCase) {
    $chars .= 'QWERTYUPASDFGHJKZXCVBNML';
  }
  if ($allowAmbiguous) {
    $chars .= 'iol';
    if ($mixedCase) {
      $chars .= 'IO';
    }
  }

  $password = '';
  foreach (range(1, $length) as $index) {
    $char = $chars[random_int(0, strlen($chars) - 1)];

    if (!$allowRepeatingCharacters) {
      while ($char == substr($password, -1)) {
        $char = $chars[random_int(0, strlen($chars) - 1)];
      }
    }

    $password .= $char;
  }


  // add numeric characters
  $takenSubstitutionIndexes = [];

  if ($numericCount > 0) {
    $chars = '23456789';
    if ($allowAmbiguous) {
      $chars .= '10';
    }

    foreach (range(1, $numericCount) as $_) {
      $index = random_int(0, strlen($password) - 1);
      while (in_array($index, $takenSubstitutionIndexes)) {
        $index = random_int(0, strlen($password) - 1);
      }

      $char = $chars[random_int(0, strlen($chars) - 1)];
      if (!$allowRepeatingCharacters) {
        while (substr($password, $index - 1, 1) == $char || substr($password, $index + 1, 1) == $char) {
          $char = $chars[random_int(0, strlen($chars) - 1)];
        }
      }

      $password[$index] = $char;
      $takenSubstitutionIndexes[] = $index;
    }
  }

  // add symbols
  $chars = '!@#$%&*=+?';
  if ($allowAmbiguous) {
    $chars .= '^~-_()[{]};:|\\/,.\'"`<>';
  }

  if ($symbolCount > 0) {
    foreach (range(1, $symbolCount) as $_) {
      $index = random_int(0, strlen($password) - 1);
      while (in_array($index, $takenSubstitutionIndexes)) {
        $index = random_int(0, strlen($password) - 1);
      }

      $char = $chars[random_int(0, strlen($chars) - 1)];
      if (!$allowRepeatingCharacters) {
        while (substr($password, $index - 1, 1) == $char || substr($password, $index + 1, 1) == $char) {
          $char = $chars[random_int(0, strlen($chars) - 1)];
        }
      }

      $password[$index] = $char;
      $takenSubstitutionIndexes[] = $index;
    }
  }

  return $password;
}

短的方法。

这里有一些生成随机字符串的最短方法

<?php
echo $my_rand_strng = substr(str_shuffle("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"), -15); 

echo substr(md5(rand()), 0, 7);

echo str_shuffle(MD5(microtime()));
?>

该函数的编辑版本工作正常，但我发现只有一个问题:您使用了错误的字符来包含$字符，因此'字符有时是生成的随机字符串的一部分。

要解决这个问题，请更改:

$characters = ’0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ’;

to:

$characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';

这种方法只使用包含的字符，'字符永远不会是生成的随机字符串的一部分。

我喜欢使用openssl_random_pseudo_bytes的最后一个注释，但这对我来说不是一个解决方案，因为我仍然必须删除我不想要的字符，而且我无法获得一个设置长度的字符串。这是我的解决方案……

function rndStr($len = 20) {
    $rnd='';
    for($i=0;$i<$len;$i++) {
        do {
            $byte = openssl_random_pseudo_bytes(1);
            $asc = chr(base_convert(substr(bin2hex($byte),0,2),16,10));
        } while(!ctype_alnum($asc));
        $rnd .= $asc;
    }
    return $rnd;
}

首先，定义你想要使用的字母:

$alphanum = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
$special  = '~!@#$%^&*(){}[],./?';
$alphabet = $alphanum . $special;

然后，使用openssl_random_pseudo_bytes()生成适当的随机数据:

$len = 12; // length of password
$random = openssl_random_pseudo_bytes($len);

最后，使用这些随机数据创建密码。因为$random中的每个字符可以是chr(0)直到chr(255)，代码使用其序数与$alphabet_length除法后的余数来确保只从字母表中选择字符(注意这样做会偏向随机性):

$alphabet_length = strlen($alphabet);
$password = '';
for ($i = 0; $i < $len; ++$i) {
    $password .= $alphabet[ord($random[$i]) % $alphabet_length];
}

或者，通常更好的方法是使用RandomLib和SecurityLib:

use SecurityLib\Strength;

$factory = new RandomLib\Factory;
$generator = $factory->getGenerator(new Strength(Strength::MEDIUM));

$password = $generator->generateString(12, $alphabet);

function gen_uid($l=5){
   return substr(str_shuffle("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"), 10, $l);
}
echo gen_uid();

默认值[5]:WvPJz

echo gen_uid(30);

价值[30]:cAiGgtf1lDpFWoVwjykNKXxv6SC4Q2