下面是源代碼，及其相關解釋

 1 <?php
 2 
 3 //URL是遠程的完整圖片地址，不能為空, $filename 是另存為的圖片名字
 4 //默認把圖片放在以此腳本相同的目錄里
 5 function GrabImage($url, $filename=""){
 6           
 7           //$url 為空則返回 false;
 8           if($url == ""){return false;}
 9           $ext = strrchr($url, ".");//得到圖片的擴展名
10           if($ext != ".gif" && $ext != ".jpg" && $ext != ".bmp"){echo "格式不支持！";return false;}
11           if($filename == ""){$filename = time()."$ext";}//以時間戳另起名
12           //開始捕捉
13           ob_start();
14           readfile($url);
15           $img = ob_get_contents();
16           ob_end_clean();
17           $size = strlen($img);
18           $fp2 = fopen($filename , "a");
19           fwrite($fp2, $img);
20           fclose($fp2);
21           return $filename;
22  
23  }
24  //測試
25 GrabImage("http://www.66xing.com/UploadFile/200609082320515027.bmp", "as.gif");
26  
27  ?>

相關描述：

ob_start : 打開輸出緩沖
This function will turn output buffering on. While output buffering is active no output is sent from the script (other than headers), instead the output is stored in an internal buffer. (輸出是在內部緩沖儲存)
 //
readfile : 讀入一個文件并寫入到輸出緩沖
返回從文件中讀入的字節數。如果出錯返回 FALSE 并且除非是以 @readfile() 形式調用，否則會顯示錯誤信息。 
//

ob_get_contents : Return the contents of the output buffer(返回輸出緩沖的內容)
This will return the contents of the output buffer without clearing it or FALSE, if output buffering isn't active. (如果輸出緩沖沒有活動（打開），則返回 FALSE)
//
ob_end_clean() : Clean (erase) the output buffer and turn off output buffering(清除輸出緩沖)
This function discards(丟棄) the contents of the topmost output buffer and turns off this output buffering.(丟棄并且關掉) If you want to further process the buffer's contents you have to call ob_get_contents() before ob_end_clean() as the buffer contents are discarded when ob_end_clean() is called. （如果要用緩沖內容，則在清理輸出緩沖之前要先調用 ob_get_contents()）The function returns TRUE when it successfully discarded one buffer and FALSE otherwise. Reasons for failure are first that you called the function without an active buffer or that for some reason a buffer could not be deleted (possible for special buffer). 

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