Detailed explanation of the queue principle in PHP and the graphic code for writing files

The examples in this article describe the PHP queue principle and queue-based file writing cases. Share it with everyone for your reference, the details are as follows:

The queue is a linear table, based on the first in first out principle:

Joining the team:

Leaving the team:

# #PHP implementation queue: The first element is the head of the queue, and the last element is the tail of the queue

<?php
/**
 * 队列就是这么简单
 *
 * @link
 */
$array = array(&#39;PHP&#39;, &#39;JAVA&#39;);
array_push($array, &#39;PYTHON&#39;); //入队列
array_shift($array); //出队列

What is a double-ended queue (or two-way queue) Deque, the full name is double -ended queue?

That is, elements can be entered or dequeued at any part of the queue. If we call these methods insertLeft() and insertRight(), as well as removeLeft() and removeRight(). If calling the insertLeft() and removeLeft() methods is strictly prohibited (or the operation of the right segment is disabled), the double-ended queue functions like a stack. It is forbidden to call insertLeft() and removeRight() (or another pair of methods on the contrary), and its function is the same as a queue. A deque is a versatile data structure compared to a stack or queue.

PHP implements double-ended queue

<?php
class Deque
{
  public $queue = array();
  /**（尾部）入队 **/
  public function addLast($value)
  {
    return array_push($this->queue,$value);
  }
  /**（尾部）出队**/
  public function removeLast()
  {
    return array_pop($this->queue);
  }
  /**（头部）入队**/
  public function addFirst($value)
  {
    return array_unshift($this->queue,$value);
  }
  /**（头部）出队**/
  public function removeFirst()
  {
    return array_shift($this->queue);
  }
  /**清空队列**/
  public function makeEmpty()
  {
    unset($this->queue);
  }
  /**获取列头**/
  public function getFirst()
  {
    return reset($this->queue);
  }
  /** 获取列尾 **/
  public function getLast()
  {
    return end($this->queue);
  }
  /** 获取长度 **/
  public function getLength()
  {
    return count($this->queue);
  }
}

Purpose of queue:

Queue can be very good Process data transmission and storage asynchronously. When you frequently insert data into the database and submit data to search engines, you can use queues to insert data asynchronously. In addition, slower processing logic and processing logic with limited concurrency can also be placed in the background for processing through message queues, such as FLV video conversion, sending mobile phone text messages, sending emails, etc.

Project Case

There is a project here. Due to server permission issues, there is no way to install the queue program, and there are more than 300 concurrent users. The service provider The maximum number of connections to the database is 300. In order to solve this problem, a simple queue program was written. The code is as follows

Read queue code:

<?php
set_time_limit(0);
$file_name3 = &#39;3.txt&#39;;//这个地方是讲队列文件读出的内容写入文件，test中代替的是mysql数据库操作
$file3 = fopen($file_name3,&#39;a&#39;);
while(true)
{
  $c = FALSE;
  $file_name = &#39;1.txt&#39;;//队列文件
  $file = fopen($file_name,&#39;r&#39;);
  if(!feof($f))
  {
    //获得第一条数据
    $a = fgets($file);
    if(!empty($a))
    {
      $c = TRUE;
      fwrite($file3,$a);//这里可以改为数据库操作
    }
  }
  fclose($file);
  if($c)
  {
    //将文件的第一条数据删除
    exec(&#39;sed -i \&#39;1d\&#39; /var/www/csv_sql/1.txt&#39;);
  }
  sleep(1);
  if(time()>=strtotime(&#39;20160416150000&#39;))
  {
    exit;
  }
}
fclose($file3);

The read queue program is actually an infinite loop program. If the closing point is not set, the loop will continue

Reading the file

Writing the queue program is relatively simple, just write the file

<?php
set_time_limit(0);
$file_name2 = &#39;2.txt&#39;;//test中用来比对队列程序是否正常的
$file2 = fopen($file_name2,&#39;a&#39;);
for($i=1;$i<11;$i++)
{
  $file_name = &#39;1.txt&#39;;//队列文件
  $file = fopen($file_name,&#39;a&#39;);//fopen的mode属性必须是a或a+
  $str = $i.&#39;--&#39;.rand(100001,999999);
  fwrite($file,$str."\n");
  fwrite($file2,$str."\n");
  sleep(1);
  fclose($file);
}
fclose($file2);

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