PHP生成随机或者唯一字符串

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/**
 * [生成随机字符串]
 * @E-mial [e-mail]
 * @TIME   2017-04-07
 * @WEB    http://blog.iinu.com.cn
 * @param  integer $length [生成的长度]
 * @param  integer $type   [生成的类型]
 * @return [type]   str       [description]
 * @php 随机码类型：0，数字+大写字母；1，数字；2，小写字母；3，大写字母；4，特殊字符；-1，数字+大小写字母+特殊字符
 */
function randCode($length = 5, $type = 0) {
 $arr = array(1 => "0123456789", 2 => "abcdefghijklmnopqrstuvwxyz", 3 => "ABCDEFGHIJKLMNOPQRSTUVWXYZ", 4 => "~@#$%^&*(){}[]|");
if ($type == 0) {
 array_pop($arr);
 $string = implode("", $arr);
} else if ($type == "-1") {
 $string = implode("", $arr);
} else {
 $string = $arr[$type];
}
 $count = strlen($string) - 1;
for ($i = 0; $i < $length; $i++) {
 $str[$i] = $string[rand(0, $count)];
 $code .= $str[$i];
}
return $code;
}

/**
 * [生成唯一字符串]
 * @E-mial [e-mail]
 * @TIME 2017-04-07
 * @WEB http://blog.iinu.com.cn
 * @ 0-存数字字符串；1-小写字母字符串；2-大写字母字符串；3-大小写数字字符串；4-字符；
 * 5-数字，小写，大写，字符混合
 * @param integer $type [字符串的类型]
 * @param integer $length [字符串的长度]
 * @param integer $time [是否带时间1-带，0-不带]
 * @return [string] $str [返回唯一字符串]
 */
function randSole($type = 0,$length = 18,$time=0){
 $str = $time == 0 ? '':date('YmdHis',time());
switch ($type) {
case 0:
for((int)$i = 0;$i <= $length;$i++){
if(mb_strlen($str) == $length){
 $str = $str;
}else{