PHP的在线用户计数器

现在我将告诉你如何看到有多少用户在浏览您的网站。有许多方法来显示它，但我试图保持它简单，干净。

首先，我们必须创建两个表，您的数据库教程。

CREATE TABLE `uonline` (
  `session` varchar(100) NOT NULL,
  `time` int(5) NOT NULL default '0'
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

这将创建两个表。一个是会议和其他的是时间。他们将我们的信息存储。

现在是PHP的时间。让我们一起创造我们的主要变数

<?php教程
session_start();
$ses = session_id();
$time = time();
$timech=$time-300;
session_start(); - This wills start a session
$ses = session_id(); - This will get our session's ID
$time = time(); - This will get the time
$timech=$time-300; - This will set our time to 5min

Now we have to connect to the database:

// Declare SQL login info
$host = "localhost";
$username = "";
$password = "";
$dbname = "";
 
// Now we are going to connect to our database
mysql教程_connect("$host", "$username", "$password")or die("<font style='color:red'><b>Can not connect:</b> ".mysql_error()."</font>");
mysql_select_db("$db_name")or die("<font style='color:red'><b>Can not select the database:</b> ".mysql_error()."</font>");

$host = "localhost"; - Your SQL's host name, usually it's "localhost"
$username = ""; - Your MySQL username
$password = ""; - Your MySQL password
$dbname = ""; - Your database's name

Now we have to look for existing sessions and get the number of sessions.

$result = mysql_query("SELECT * FROM uonline WHERE session='$ses'");
$num = mysql_num_rows($result); 

$result = mysql_query("SELECT * FROM uonline WHERE session='$ses'"); - This will select all info from session column where it's value is "$ses"
$num = mysql_num_rows($result); - It will tell us how many active records are in session column

if($num == "0"){
$result1 = mysql_query("INSERT INTO uonline (session, time)VALUES('$ses', '$time')");
}else{
$result2 = mysql_query("UPDATE uonline SET time='$time' WHERE session = '$ses'");
}

if($num=="0"){ - If there's no records in session column then we must insert some records
$result1 = mysql_query("INSERT INTO uonline (session, time)VALUES('$ses', '$time')"); - Inserts session's ID and time to database
}else{ - But if there was more records than 0, let's update their records
$result2 = mysql_query("UPDATE uonline SET time='$time' WHERE session = '$ses'"); - Updates existing records
} - Ends If statement

Now let's find our info again from the columns:

$result3 = mysql_query("SELECT * FROM uonline");

$result3 = mysql_query("SELECT * FROM uonline"); - This will get all info from uonline table

It's time for showing how many users are looking your site:

$usersonline = mysql_num_rows($result3);
echo "There are: <b>".$usersonline."</b> users online";

$usersonline = mysql_num_rows($result3); - It will get the number of records in columns
echo "There are: <b>".$usersonline."</b> users online"; - This will show how many users are on your site

When the users have left, you must delete their records from database.

mysql_query("DELETE FROM uonline WHERE time<$timech");
?>

mysql_query("DELETE FROM uonline WHERE time<$timech"); - Deletes records from database when 5min has been thru.

And here's the full code:

<?php
session_start();
$ses = session_id();
$time = time();
$timech=$time-300; 
 
$host = "localhost";
$username = "";
$password = "";
$dbname = "";
 
mysql_connect("$host", "$username", "$password")or die("<font style='color:red'><b>Can not connect:</b> ".mysql_error()."</font>");
mysql_select_db("$db_name")or die("<font style='color:red'><b>Can not select the database:</b> ".mysql_error()."</font>");  
 
$result = mysql_query("SELECT * FROM uonline WHERE session='$ses'");
$num = mysql_num_rows($result); 
 
if($num == "0"){
$result1 = mysql_query("INSERT INTO uonline (session, time)VALUES('$ses', '$time')");
}else{
$result2 = mysql_query("UPDATE uonline SET time='$time' WHERE session = '$ses'");
} 
 
$result3 = mysql_query("SELECT * FROM uonline"); 
 
$usersonline = mysql_num_rows($result3);
echo "There are: <b>".$usersonline."</b> users online";  
 
mysql_query("DELETE FROM uonline WHERE time<$timech");
?>

<?php
require ('resize_img.php');
//how to use the class:
//makes a simple thumbnail of an image of 100x100 and saves the image then outputs it.
$imgresize = new resize_img();

$imgresize->sizelimit_x = 100;
$imgresize->sizelimit_y = 100;
$imgresize->keep_proportions = true;
$imgresize->output = 'PNG';

if( $imgresize->resize_image( 'C:/xampp/htdocs/wannabe/image_bin/public/treeshadows_001.gif' ) === false )
{
  echo 'ERROR!';
}
else
{
  $imgresize->save_resizedimage( 'C:/xampp/htdocs/wannabe/image_bin/public/thumbnails/', 'treeshadows_001' );
  $imgresize->output_resizedimage();
}

$imgresize->destroy_resizedimage();

?>

// resize_img.php文件

<?php

/**
 * by Daniel M. Story <admin@danstory.com>
 */

class resize_img
{
  var $image_path = '';
  //holds the image path
  var $sizelimit_x = 250;
  //the limit of the image width
  var $sizelimit_y = 250;
  //the limit of the image height
  var $image_resource = '';
  //holds the image resource
  var $keep_proportions = true;
  //if true it keeps教程 the image proportions when resized
  var $resized_resource = '';
  //holds the resized image resource
  var $hasGD = false;
  var $output = 'SAME';
  //can be JPG, GIF, PNG, or SAME (same will save as old type)
 
  function resize_img()
  {
    if( function_exists('gd_info') ){ $this->hasGD = true; } 
  }
 
  function resize_image( $image_path )
  {
    if( $this->hasGD === false ){ return false; }
    //no GD installed on the server!
   
    list($img_width, $img_height, $img_type, $img_attr) = @getimagesize( $image_path );
    //this is going to get the image width, height, and format
   
    if( ( $img_width != 0 ) || ( $img_width != 0 ) )
    //make sure it was loaded correctly
    {
      switch( $img_type )
      {
        case 1:
          //GIF
          $this->image_resource = @imagecreatefromgif( $image_path );
          if( $this->output == 'SAME' ){ $this->output = 'GIF'; }
          break;
        case 2:
          //JPG
          $this->image_resource = @imagecreatefromjpeg( $image_path );
          if( $this->output == 'SAME' ){ $this->output = 'JPG'; }
          break; 
        case 3:
          //PNG
          $this->image_resource = @imagecreatefrompng( $image_path );
          if( $this->output == 'SAME' ){ $this->output = 'PNG'; }
      }
      if( $this->image_resource === '' ){ return false; }
      //it wasn't able to load the image
    }
    else{ return false; }
    //something happened!
   
    if( $this->keep_proportions === true )
    {
      if( ($img_width-$this->sizelimit_x) > ($img_height-$this->sizelimit_y) )
      {
      //if the width of the img is greater than the size limit we scale by width
        $scalex = ( $this->sizelimit_x / $img_width );
        $scaley = $scalex;
      }
      else
      //if the height of the img is greater than the size limit we scale by height
      {
        $scalex = ( $this->sizelimit_y / $img_height );
        $scaley = $scalex;
      }

    }
    else
    {
      $scalex = ( $this->sizelimit_x / $img_width );
      $scaley = ( $this->sizelimit_y / $img_height );
      //just make the image fit the image size limit
     
      if( $scalex > 1 ){ $scalex = 1; }
      if( $scaley > 1 ){ $scaley = 1; }
      //don't make it so it streches the image
    }
   
    $new_width = $img_width * $scalex;
    $new_height = $img_height * $scaley;
   
    $this->resized_resource = @imagecreatetruecolor( $new_width, $new_height );
    //creates an image resource, with the width and height of the size limits (or new resized proportion )
   
    if( function_exists( 'imageantialias' )){ @imageantialias( $this->resized_resource, true ); }
    //helps in the quality of the image being resized
   
    @imagecopyresampled( $this->resized_resource, $this->image_resource, 0, 0, 0, 0, $new_width, $new_height, $img_width, $img_height );
    //resize the iamge onto the resized resource
   
    @imagedestroy( $this->image_resource );
    //destory old image resource
   
    return true;
  }
 
  function save_resizedimage( $path, $name )
  {
    switch( strtoupper($this->output) )
    {
      case 'GIF':
        //GIF
        @imagegif( $this->resized_resource, $path . $name . '.gif' );
        break;
      case 'JPG':
        //JPG
        @imagejpeg( $this->resized_resource, $path . $name . '.jpg' );
        break; 
      case 'PNG':
        //PNG
        @imagepng( $this->resized_resource, $path . $name . '.png' );
    }
  }
 
  function output_resizedimage()
  {
    $the_time = time();
    header('Last-Modified: ' . date( 'D, d M Y H:i:s', $the_time ) . ' GMT');
    header('Cache-Control: public');
   
    switch( strtoupper($this->output) )
    {
      case 'GIF':
        //GIF
        header('Content-type: image/gif');
        @imagegif( $this->resized_resource );
        break;
      case 'JPG':
        //JPG
        header('Content-type: image/jpg');
        @imagejpeg( $this->resized_resource );
        break; 
      case 'PNG':
        //PNG
        header('Content-type: image/png');
        @imagepng( $this->resized_resource );
    }
  }
 
  function destroy_resizedimage()
  {
    @imagedestroy( $this->resized_resource );
    @imagedestroy( $this->image_resource );
  }

}

?>

此脚本时，页面最后修订和产出作为二十分钟前，或XX天前的日期...或者即使您不更新太多 - 二十周前显示！

//File Name
$last_modified = filemtime("FILE.php");
 
{
$timediff = time() - $last_modified;
 
if ($timediff < 3600)
{
if ($timediff < 120)
{
$returndate = "1 minute ago.";
}
else
{
$returndate = intval($timediff / 60) . " minutes ago.";
}
}
else if ($timediff < 7200)
{
$returndate = "1 hour ago.";
}
else if ($timediff < 86400)
{
$returndate = intval($timediff / 3600) . " hours ago.";
}
else if ($timediff < 172800)
{
$returndate = "1 day ago.";
}
else if ($timediff < 604800)
{
$returndate = intval($timediff / 86400) . " days ago.";
}
 
else if ($timediff < 1209600)
{
$returndate = "1 week ago.";
}
else if ($timediff < 3024000)
{
$returndate = intval($timediff / 604900) . " weeks ago.";
}
else
{
$returndate = @date('n-j-Y', $timestamp);
if($type=="fulldate")
{
$returndate = @date('n-j-y, H:i', $timestamp);
 
}
 
else if ($type=="time")
{
 
$returndate = @date('H:i', $timestamp);
 
}
 
}
//Display It
print("Last Modified: ");
print($returndate);
 
}
?>

它应该很容易理解。

$ last_modified = filemtime（“FILE.php”）; - 更改FILE.php到文件您要连接。

确定了PHP脚本所需的时间执行正确的一微秒。

插入在页面顶部的代码：

<?php 
          $mtime = microtime(); 
          $mtime = explode(' ', $mtime); 
          $mtime = $mtime[1] + $mtime[0]; 
          $starttime = $mtime; 
?>
然后添加在页面底部的以下内容：

<?php 
          $mtime = microtime(); 
          $mtime = explode(" ", $mtime); 
          $mtime = $mtime[1] + $mtime[0]; 
          $endtime = $mtime; 
          $totaltime = ($endtime - $starttime); 
          echo 'This page was created in ' .$totaltime. ' seconds.'; 
?>

PHP的microtime中（）函数返回当前的Unix时间戳微秒。

有时，您可能希望让无条件循环的开始，并允许括号内的语句来决定何时退出循环。

有两个特殊的语句可用在循环使用：中断和继续。

break语句终止或For循环的同时，继续执行现行的代码如下循环后（如有）。或者，

你可以把一个数字后，折价关键字，说明如何循环结构的多层次，以摆脱。这样，埋

藏在一份声明中深层嵌套的循环可以打破最外层循环。

<?php
echo "<p><b>Example of using the Break statement:</b></p>";

for ($i=0; $i<=10; $i++) {
   if ($i==3){break;}
   echo "The number is ".$i;
   echo "<br />";
}

echo "<p><b>One more example of using the Break statement:</b><p>";

$i = 0;
$j = 0;

while ($i < 10) {
  while ($j < 10) {
    if ($j == 5) {break 2;} // breaks out of two while loops教程
    $j++;
  }
  $i++;
}

echo "The first number is ".$i."<br />";
echo "The second number is ".$j."<br />";
?>

continue语句终止了在语句块执行一或For循环的同时，继续对下一个迭代循环的执行

：

<?php
echo "<p><b>Example of using the Continue statement:</b><p>";

for ($i=0; $i<=10; $i++) {
   if (i==3){continue;}
   echo "The number is ".$i;
   echo "<br />";
}
?>