PHP设置图片浏览器缓存方法介绍

HTTP/1.1 200 OK
Date: Tue, 03 Mar 2009 04:58:40 GMT
Content-Type: image/jpeg
Content-Length: 83185
Last-Modified: Tue, 24 Feb 2009 08:01:04 GMT
Cache-Control: max-age=2592000
Expires: Thu, 02 Apr 2009 05:14:08 GMT
Etag: “5d8c72a5edda8d6a:3239″

HTTP/1.x 304 Not Modified
Date: Tue, 03 Mar 2009 05:03:56 GMT
Content-Type: image/jpeg
Content-Length: 83185
Last-Modified: Tue, 24 Feb 2009 08:01:04 GMT
Cache-Control: max-age=2592000
Expires: Thu, 02 Apr 2009 05:14:08 GMT
Etag: “5d8c72a5edda8d6a:3239″

header(’Cache-Control: max-age=86400,must-revalidate’);
header(’Last-Modified: ‘ .gmdate(’D, d M Y H:i:s’) . ‘ GMT’ );
header(”Expires: ” .gmdate (’D, d M Y H:i:s’, time() + ‘86400′ ). ‘ GMT’);

cache();
echo date(”Y-m-d H:i:s”);
function cache()
{
       $etag = “http://longrujun.name”;
       if (isset($_SERVER['HTTP_IF_NONE_MATCH'])  &&
$_SERVER['HTTP_IF_NONE_MATCH'] == $etag)
       {
              header(’Etag:’.$etag,true,304);
              exit;
       }
       else header(’Etag:’.$etag);
}

$imagePath = "path/to/some/image";
 
$eTag = $imagePath;
$eTag .= fileMTime($imagePath);
$eTag = md5($eTag);
 
if((isset($_SERVER['HTTP_IF_NONE_MATCH'])) &&
(stripslashes($_SERVER['HTTP_IF_NONE_MATCH']) == $eTag)) {
    header("HTTP/1.1 304 Not Modified", TRUE, 304);
    exit();
}
 
header("ETag: ".$eTag);
header("Content-Type: image/png");
readFile($imagePath);
exit();

$fullpath = '/www/images/' . basename($_GET['img']); //假定文件都在/www/images/下
if (!is_file($fullpath)) {
    header("HTTP/1.0 404 Not Found");
    exit();
}
 
$info = getImageSize($fullpath); //获取图片信息
if (!$info) {                    //如果不是图片
    header("HTTP/1.0 404 Not Found");
    exit();
}
 
// 以下凡是header函数都是在输出头部信息。较多。
header('Content-type: '. $info['mime']);          //类似于image/png
header('Content-Length: '. filesize($fullpath));  //文件长度
 
header('Pragma: ');             //没用，但要设置，防止服务器生成no-cache的可怕字眼
 
//手动设置过期时间，单位都是秒
$validtime = 48* 60 * 60;    // 48小时
 
//缓存相对请求的时间，
header('Cache-Control: ' . 'max-age='. $validtime);
 
//也很重要的Expires头，功能类似于max-age
//time()+$validtime: 设置期限，到期后才会向服务器提交请求
//gmdate，生成Sun, 01 Mar 2009 04:05:49 +0000  的字符串，而且是GMT标准时区
//preg_replace,  生成Sun, 01 Mar 2009 04:05:49 GMT， 注意：可能与服务器设置有关，
//但我都用默认设置
header('Expires:'. preg_replace('/.{5}$/', 'GMT', gmdate('r', time()+ $validtime)));
 
//文件最后修改时间
$lasttime = filemtime($fullpath);
 
//最后修改时间，设置了，点击刷新时，浏览器再次请求图片才会发出'IF_MODIFIED_SINCE'头，
//从而被php程序读取
header('Last-Modified: ' . preg_replace('/.{5}$/', 'GMT', gmdate('r', $lasttime) ));
 
//重要，如果请求中的时间和 文件生成时间戳相等，则文件未修改，客户端可用缓存
if (strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE']) == $lasttime) {
    header("HTTP/1.1 304 Not Modified"); //服务器发出文件不曾修改的指令
    exit();
}
 
//如果文件被修改了，只好重新发出数据
echo file_get_contents($fullpath);

<?php
$a = 1;
$b = 2;

function Sum()
{
    global $a, $b; //在里面声明为全局变量

    $b = $a + $b;
}

Sum();
echo $b;
?>

 <?PHP
      $w3sky = 1;
      $w3sky2 = 2;

function Sum()
       {
       global $w3sky, $w3sky2;$w3sky2 = $w3sky + $w3sky2;
       }Sum();
       echo $w3sky2;
       ?>

<?php
echo memory_get_usage();
$var=str_repeat(www.111cn.net,10000);
echo memory_get_usage();
unset($var);
echo memory_get_usage();
?>

<?php

$t1 = microtime(true);
$m1 = memory_get_usage(true);
echo fixByte($m1). '<br />';

/*↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓*/

/*↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑*/

$t2 = microtime(true);
$m2 = memory_get_usage(true);
echo '<br />' . fixByte($m2). '<br />';

echo '<hr >';
echo 'time ' . round(($t2 - $t1), 4) .'<br />';
echo 'mem ' . fixByte($m2 - $m1) .  '<br />';

/**
 * 格式化字节为合适的数值
 * @param int $byte 字节数
 * @param string $string 格式化的可读性强的字节数
 */
function fixByte($byte, $string = true, $dot_num = 9) {
 $ret = array(
   'data'=>$byte,
   'danwei'=>'Byte',
 );

 if ($byte < 1024) {

 } else if ($byte < 1024*1024) {
  $ret['data'] = round($byte / 1024, $dot_num);
  $ret['danwei']='K';
 } else if ($byte < 1024*1024*1024) {
  $ret['data'] = round($byte / (1024*1024), $dot_num);
  $ret['danwei']='M';
 } else if ($byte < 1024*1024*1024*1024) {
  $ret['data'] = round($byte / (1024*1024*1024), $dot_num);
  $ret['danwei']='GB';
 } else if ($byte < 1024*1024*1024*1024*1024) {
  $ret['data'] = round($byte / (1024*1024*1024*1024), $dot_num);
  $ret['danwei']='TB';
 }

 if ($string) {
  $ret = $ret['data'] . ' ' . $ret['danwei'];
 }

 return $ret;
}

<?php
function code62($x){
 $show='';
 while($x>0){
  $s=$x % 62;
  if ($s>35){
   $s=chr($s+61);
  }elseif($s>9&&$s<=35){
   $s=chr($s+55);
  }
  $show.=$s;
  $x=floor($x/62);
 }
 return $show;
}
function shorturl($url){
 $url=crc32($url);
 $result=sprintf("%u",$url);
 return code62($result);
}

如何将

http://z.cn/link.php?url=http://www.111cn.net

缩成

http://z.cn/zHEYrvV

RewriteEngine On 

RewriteBase / 

RewriteRule ^/(.*)$ link.php?url=$1[L]

array(2) {
[0]=>
array(2) {
["url"]=>
string(52) “http://127.0.0.1/testforum.cityofsteam.com/index.php”
["name"]=>
string(28) “City of Steam Official Forum”
}
[2]=>
array(2) {
["url"]=>
string(62) “http://127.0.0.1/testforum.cityofsteam.com/index.php?board=4.0″
["name"]=>
string(12) “Announcement”
}
}

Array ( [0] => apple [1] => banana [3] => dog )

<?php

function array_remove(&$arr, $offset)

{
 
array_splice($arr, $offset, 1);

}

$arr = array('apple','banana','cat','dog');
 
array_remove($arr, 2);
 
print_r($arr);

?>

Array ( [0] => apple [1] => banana [2] => dog )

<?php
$a = array('1.10', 12.4, 1.13);

if (in_array('12.4', $a, true)) {
    echo "'12.4' found with strict checkn";
}
if (in_array(1.13, $a, true)) {
    echo "1.13 found with strict checkn";
}
?>
上例将输出：

1.13 found with strict check

<?php
$a = array(array('p', 'h'), array('p', 'r'), 'o');

if (in_array(array('p', 'h'), $a)) {
    echo "'ph' was foundn";
}
if (in_array(array('f', 'i'), $a)) {
    echo "'fi' was foundn";
}
if (in_array('o', $a)) {
    echo "'o' was foundn";
}
?>
上例将输出：

  'ph' was found
  'o' was found