php生成短域名函数

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public function createRandCode($string) {

$code = '';

$hex_code = '1qaz2wsx3edc4rfv5t-gb6yhn7ujm8ik9ol0p_';

$now = microtime(true) * 10000;

$strlen = strlen($hex_code);

$hash_code = hash('sha256', $string);

// 这里会为编码定义一个随机的长度，长度取决于step

$step = rand(8, 16);

$count = ceil(strlen($hash_code) / $step);

for($i = 0; $i < $count; $i++) {

$start = $i * $step;

$hex_num = substr($hash_code, $start, $step);

$num = 0x3fffffff & (1 * '0x' . $hex_num);

$n = $num % $strlen;

$code .= $hex_code[$n];

}

return $code;

}