如何利用php数组对百万数据进行排重
如何利用php数组对百万数据进行排重
在平时的工作中,经常接到要对网站的会员进行站内信、手机短信、email进行群发信息的通知,用户列表一般由别的同事提供,当中难免会有重复,为了避免重复发送,所以我在进行发送信息前要对他们提供的用户列表进行排重,下面我以uid列表来讲讲我是如何利用php数组进行排重的。
假如得到一个uid列表,数量在百万行以上,格式如下:
10001000
10001001
10001002
................
10001000
................
10001111
其实利用php数组的特性,很好进行排重,我们先来看一下php数组的定义:PHP 中的数组实际上是一个有序映射。映射是一种把 values 关联到 keys 的类型。此类型在很多方面做了优化,因此可以把它当成真正的数组,或列表(向量),散列表(是映射的一种实现),字典,集合,栈,队列以及更多可能性。数组元素的值也可以是另一个数组。树形结构和多维数组也是允许的。
在php的数组中,键(keys)也称为索引,具有唯一性,我们正可以利用这一特性进行排重,示例代码如下:
<?php //定义一个数组,用于存放排重后的结果 $result = array(); //读取uid列表文件 $fp = fopen('test.txt', 'r'); while(!feof($fp)) { $uid = fgets($fp); $uid = trim($uid); $uid = trim($uid, "r"); $uid = trim($uid, "n"); if($uid == '') { continue; } //以uid为key去看该值是否存在 if(empty($result[$uid])) { $result[$uid] = 1; } } fclose($fp); //将结果保存到文件 $content = ''; foreach($result as $k => $v) { $content .= $k."n"; } $fp = fopen('result.txt', 'w'); fwrite($fp, $content); fclose($fp); ?> Copy after login |
还有,这可方法还可以用于两个文件进行排重的工作,如果你有两个uid列表文件,格式和上面的uid列表一样,示例程序如下:
<p><table cellspacing="0" cellpadding="6" width="95%" align="center" border="0" style="border-right: #0099cc 1px solid; table-layout: fixed; border-top: #0099cc 1px solid; border-left: #0099cc 1px solid; border-bottom: #0099cc 1px solid"><tbody><tr><td bgcolor="#ddedfb" style="word-wrap: break-word"><pre class="code"> <?php //定义数组,用于存放排重后的结果 $result = array(); //读取第一个uid列表文件,放入$result_1 $fp = fopen('test_1.txt', 'r'); while(!feof($fp)) { $uid = fgets($fp); $uid = trim($uid); $uid = trim($uid, "r"); $uid = trim($uid, "n"); if($uid == '') { continue; } //以uid为key写入$result,如有重复就会覆盖 $result[$uid] = 1; } fclose($fp); //读取第二个uid列表文件,并进行排重操作 $fp = fopen('test_2.txt', 'r'); while(!feof($fp)) { $uid = fgets($fp); $uid = trim($uid); $uid = trim($uid, "r"); $uid = trim($uid, "n"); if($uid == '') { continue; } //以uid为key去看该值是否存在 if(empty($result[$uid])) { $result[$uid] = 1; } } fclose($fp); //$result里保存的就排重以后的结果,可以输出到文件,代码省略 ?>
仔细想想,不难发现,利用数组的这一特性还可以解决我们工作中的更多问题。

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