使用PHP开发应用程序，尤其是网站程序，常常需要生成随机密码，如用户注册生成随机密码，用户重置密码也需要生成一个随机的密码。随机密码也就是一串固定长度的字符串，这里我收集整理了几种生成随机字符串的方法，以供大家参考。
方法一：
1、在 33 – 126 中生成一个随机整数，如 35，
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2、将 35 转换成对应的ASCII码字符，如 35 对应 #
3、重复以上 1、2 步骤 n 次，连接成 n 位的密码
该算法主要用到了两个函数，mt_rand ( int $min , int $max )函数用于生成随机整数，其中 $min – $max 为 ASCII 码的范围，这里取 33 -126 ，可以根据需要调整范围，如ASCII码表中 97 – 122 位对应 a – z 的英文字母，具体可参考 ASCII码表； chr ( int $ascii )函数用于将对应整数 $ascii 转换成对应的字符。
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<ol><li><span><span>function</span><span> create_password(</span><span>$pw_length</span><span> = 8) </span></span></li><li><span>{ </span></li><li><span> <span>$randpwd</span><span> = </span><span>''</span><span>; </span></span></li><li><span> <span>for</span><span> (</span><span>$i</span><span> = 0; </span><span>$i</span><span> < </span><span>$pw_length</span><span>; </span><span>$i</span><span>++) </span></span></li><li><span> { </span></li><li><span> <span>$randpwd</span><span> .= </span><span>chr</span><span>(mt_rand(33, 126)); </span></span></li><li><span> } </span></li><li><span> <span>return</span><span> </span><span>$randpwd</span><span>; </span></span></li><li><span>} </span></li><li><span> </span></li><li><span><span>// 调用该函数，传递长度参数$pw_length = 6</span><span> </span></span></li><li><span><span>echo</span><span> create_password(6); </span></span></li></ol>方法二：
1、预置一个的字符串 $chars ，包括 a – z，A – Z，0 – 9，以及一些特殊字符
2、在 $chars 字符串中随机取一个字符
3、重复第二步 n 次，可得长度为 n 的密码
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<ol><li><span><span>function</span><span> generate_password( </span><span>$length</span><span> = 8 ) { </span></span></li><li><span> <span>// 密码字符集，可任意添加你需要的字符</span><span> </span></span></li><li><span> <span>$chars</span><span> = </span><span>'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789!@#$%^&*()-_ []{}<>~`+=,.;:/?|'</span><span>; </span></span></li><li><span> </span></li><li><span> <span>$password</span><span> = </span><span>''</span><span>; </span></span></li><li><span> <span>for</span><span> ( </span><span>$i</span><span> = 0; </span><span>$i</span><span> < </span><span>$length</span><span>; </span><span>$i</span><span>++ ) </span></span></li><li><span> { </span></li><li><span> <span>// 这里提供两种字符获取方式</span><span> </span></span></li><li><span> <span>// 第一种是使用 substr 截取$chars中的任意一位字符；</span><span> </span></span></li><li><span> <span>// 第二种是取字符数组 $chars 的任意元素</span><span> </span></span></li><li><span> <span>// $password .= substr($chars, mt_rand(0, strlen($chars) - 1), 1);</span><span> </span></span></li><li><span> <span>$password</span><span> .= </span><span>$chars</span><span>[ mt_rand(0, </span><span>strlen</span><span>(</span><span>$chars</span><span>) - 1) ]; </span></span></li><li><span> } </span></li><li><span> </span></li><li><span> <span>return</span><span> </span><span>$password</span><span>; </span></span></li><li><span>} </span></li></ol>方法三：
1、预置一个的字符数组 $chars ，包括 a – z，A – Z，0 – 9，以及一些特殊字符
2、通过array_rand()从数组 $chars 中随机选出 $length 个元素
3、根据已获取的键名数组 $keys，从数组 $chars 取出字符拼接字符串。该方法的缺点是相同的字符不会重复取。
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<ol><li><span><span>function</span><span> make_password( </span><span>$length</span><span> = 8 ) </span></span></li><li><span>{ </span></li><li><span> <span>// 密码字符集，可任意添加你需要的字符</span><span> </span></span></li><li><span> <span>$chars</span><span> = </span><span>array</span><span>(</span><span>'a'</span><span>, </span><span>'b'</span><span>, </span><span>'c'</span><span>, </span><span>'d'</span><span>, </span><span>'e'</span><span>, </span><span>'f'</span><span>, </span><span>'g'</span><span>, </span><span>'h'</span><span>, </span></span></li><li><span> <span>'i'</span><span>, </span><span>'j'</span><span>, </span><span>'k'</span><span>, </span><span>'l'</span><span>,</span><span>'m'</span><span>, </span><span>'n'</span><span>, </span><span>'o'</span><span>, </span><span>'p'</span><span>, </span><span>'q'</span><span>, </span><span>'r'</span><span>, </span><span>'s'</span><span>, </span></span></li><li><span> <span>'t'</span><span>, </span><span>'u'</span><span>, </span><span>'v'</span><span>, </span><span>'w'</span><span>, </span><span>'x'</span><span>, </span><span>'y'</span><span>,</span><span>'z'</span><span>, </span><span>'A'</span><span>, </span><span>'B'</span><span>, </span><span>'C'</span><span>, </span><span>'D'</span><span>, </span></span></li><li><span> <span>'E'</span><span>, </span><span>'F'</span><span>, </span><span>'G'</span><span>, </span><span>'H'</span><span>, </span><span>'I'</span><span>, </span><span>'J'</span><span>, </span><span>'K'</span><span>, </span><span>'L'</span><span>,</span><span>'M'</span><span>, </span><span>'N'</span><span>, </span><span>'O'</span><span>, </span></span></li><li><span> <span>'P'</span><span>, </span><span>'Q'</span><span>, </span><span>'R'</span><span>, </span><span>'S'</span><span>, </span><span>'T'</span><span>, </span><span>'U'</span><span>, </span><span>'V'</span><span>, </span><span>'W'</span><span>, </span><span>'X'</span><span>, </span><span>'Y'</span><span>,</span><span>'Z'</span><span>, </span></span></li><li><span> <span>'0'</span><span>, </span><span>'1'</span><span>, </span><span>'2'</span><span>, </span><span>'3'</span><span>, </span><span>'4'</span><span>, </span><span>'5'</span><span>, </span><span>'6'</span><span>, </span><span>'7'</span><span>, </span><span>'8'</span><span>, </span><span>'9'</span><span>, </span><span>'!'</span><span>, </span></span></li><li><span> <span>'@'</span><span>,</span><span>'#'</span><span>, </span><span>'$'</span><span>, </span><span>'%'</span><span>, </span><span>'^'</span><span>, </span><span>'&'</span><span>, </span><span>'*'</span><span>, </span><span>'('</span><span>, </span><span>')'</span><span>, </span><span>'-'</span><span>, </span><span>'_'</span><span>, </span></span></li><li><span> <span>'['</span><span>, </span><span>']'</span><span>, </span><span>'{'</span><span>, </span><span>'}'</span><span>, </span><span>'<'</span><span>, </span><span>'>'</span><span>, </span><span>'~'</span><span>, </span><span>'`'</span><span>, </span><span>'+'</span><span>, </span><span>'='</span><span>, </span><span>','</span><span>, </span></span></li><li><span> <span>'.'</span><span>, </span><span>';'</span><span>, </span><span>':'</span><span>, </span><span>'/'</span><span>, </span><span>'?'</span><span>, </span><span>'|'</span><span>); </span></span></li><li><span> </span></li><li><span> <span>// 在 $chars 中随机取 $length 个数组元素键名</span><span> </span></span></li><li><span> <span>$keys</span><span> = </span><span>array_rand</span><span>(</span><span>$chars</span><span>, </span><span>$length</span><span>); </span></span></li><li><span> </span></li><li><span> <span>$password</span><span> = </span><span>''</span><span>; </span></span></li><li><span> <span>for</span><span>(</span><span>$i</span><span> = 0; </span><span>$i</span><span> < </span><span>$length</span><span>; </span><span>$i</span><span>++) </span></span></li><li><span> { </span></li><li><span> <span>// 将 $length 个数组元素连接成字符串</span><span> </span></span></li><li><span> <span>$password</span><span> .= </span><span>$chars</span><span>[</span><span>$keys</span><span>[</span><span>$i</span><span>]]; </span></span></li><li><span> } </span></li><li><span> </span></li><li><span> <span>return</span><span> </span><span>$password</span><span>; </span></span></li><li><span>} </span></li></ol>方法四：
本方法是本文被蓝色理想转载后，一名网友提供的一个新方法，算法简单，代码简短，只是因为md5()函数的返回值的缘故，生成的密码只包括字母和数字，不过也算是一个不错的方法。算法思想：
1、time() 获取当前的 Unix 时间戳
2、将第一步获取的时间戳进行 md5() 加密
3、将第二步加密的结果，截取 n 位即得想要的密码
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<ol><li><span><span>function</span><span> get_password( </span><span>$length</span><span> = 8 ) </span></span></li><li><span>{ </span></li><li><span> <span>$str</span><span> = </span><span>substr</span><span>(md5(time()), 0, 6); </span></span></li><li><span> <span>return</span><span> </span><span>$str</span><span>; </span></span></li><li><span>} </span></li></ol>时间效率对比
我们使用以下PHP代码，计算上面的 4 个随机密码生成函数生成 6 位密码的运行时间，进而对他们的时间效率进行一个简单的对比。
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<ol><li><span><span><?php </span></span></li><li><span><span>function</span><span> getmicrotime() </span></span></li><li><span>{ </span></li><li><span> list(<span>$usec</span><span>, </span><span>$sec</span><span>) = </span><span>explode</span><span>(</span><span>" "</span><span>,microtime()); </span></span></li><li><span> <span>return</span><span> ((float)</span><span>$usec</span><span> + (float)</span><span>$sec</span><span>); </span></span></li><li><span>} </span></li><li><span> </span></li><li><span><span>// 记录开始时间</span><span> </span></span></li><li><span><span>$time_start</span><span> = getmicrotime(); </span></span></li><li><span> </span></li><li><span><span>// 这里放要执行的PHP代码，如:</span><span> </span></span></li><li><span><span>// echo create_password(6);</span><span> </span></span></li><li><span> </span></li><li><span><span>// 记录结束时间</span><span> </span></span></li><li><span><span>$time_end</span><span> = getmicrotime(); </span></span></li><li><span><span>$time</span><span> = </span><span>$time_end</span><span> - </span><span>$time_start</span><span>; </span></span></li><li><span> </span></li><li><span> <span>// 输出运行总时间 </span><span> </span></span></li><li><span><span>echo</span><span> </span><span>"执行时间 $time seconds"</span><span>; </span></span></li><li><span>?> </span></li></ol>最终得出的结果是：
方法一：9.8943710327148E-5 秒
方法二：9.6797943115234E-5 秒
方法三：0.00017499923706055 秒
方法四：3.4093856811523E-5 秒
可以看出方法一和方法二的执行时间都差不多，方法四运行时间最短，而方法三的运行时间稍微长点。
以上就介绍了PHP生成随机密码的4种方法及性能对比，包括了方面的内容，希望对PHP教程有兴趣的朋友有所帮助。
