PHP檔案上傳功能 -- 單檔案上傳
這一節內容主要介紹PHP上傳檔案的單檔案上傳功能。
PHP主要通過POST方法來上傳檔案，檔案上傳之後存放在伺服器的臨時目錄下（可查看PHP設定檔php.ini中的選項upload_tmp_dir）
接下來，我們來看一例子：
----------------------------------------------------------------------
if(isset($_POST['submit'])){
switch($_FILES['upload_file']['error']){
case UPLOAD_ERR_INI_SIZE:
echo "檔案大小超過了伺服器的限制";
break;
case UPLOAD_ERR_FORM_SIZE:
echo "檔案大小超過了瀏覽器的限制";
break;
case UPLOAD_ERR_PARTIAL:
echo "只上傳了部分檔案";
break;
case UPLOAD_ERR_NO_FILE:
echo "沒有檔案被上傳";
break;
case UPLOAD_ERR_NO_TMP_DIR:
echo "找不到臨時檔案夾";
break;
case UPLOAD_ERR_CANT_WRITE:
echo "檔案寫入失敗";
break;
case UPLOAD_ERR_OK:
$upload_dir = './'.iconv("UTF-8","gb2312",$_FILES['upload_file']['name']);
if(file_exists($upload_dir)){
echo '';
}else{
if(move_uploaded_file($_FILES['upload_file']['tmp_name'],$upload_dir)){
echo '';
}else{
echo '';
}
}
break;
}
}
?>
---------------------------------------------------------------------
我們先分析一下代碼：
1、我們看到代碼中包含有$_FILES['upload_file']['error']之類的變數，那麼這是什麼意思呢？
$_FILES是一個全域二維數組，包含了上傳檔案的所有資訊。這個數組有5個元素，分別描述了上傳檔案的屬性：
$_FILES['upload_file']['name'] 上傳檔案的名稱
$_FILES['upload_file']['type'] 上傳檔案的MIME類型
$_FILES['upload_file']['size'] 上傳檔案的大小（單位：位元組）
$_FILES['upload_file']['tmp_name'] 上傳檔案的臨時名稱
$_FILES['upload_file']['error'] 上傳狀態代碼
2、我們看到代碼中包含有 UPLOAD_ERR_PARTIAL 之類的名稱，那麼這又是什麼意思呢？
這些就是上傳狀態代碼：
UPLOAD_ERR_INI_SIZE 檔案大小超過了伺服器的限制，設定 php.ini 中的 upload_max_filesize
UPLOAD_ERR_FORM_SIZE 檔案大小超過了瀏覽器的限制，設定 MAX_FILE_SIZE 隱藏表單域參數
UPLOAD_ERR_PARTIAL 檔案只上傳了一部分
UPLOAD_ERR_NO_FILE 上傳表單中沒有指定檔案
UPLOAD_ERR_NO_TMP_DIR 找不到臨時檔案
UPLOAD_ERR_CANT_WRITE 檔案寫入失敗
UPLOAD_ERR_OK 檔案上傳成功
代碼執行效果：
3、代碼中的move_uploaded_file（）函數有什麼作用？
因為檔案上傳後會被存放在伺服器的臨時目錄下，這時候就需要利用move_uploaded_file（）將其移動到指定位置上。
注意：若檔案上傳失敗，可能是 php 設定檔中的某些參數沒有設定合適，
例如File Uploads中的
; Whether to allow HTTP file uploads.
; http://php.net/file-uploads
file_uploads = On
; Temporary directory for HTTP uploaded files (will use system default if not
; specified).
; http://php.net/upload-tmp-dir
upload_tmp_dir = "\xampp\tmp"
; Maximum allowed size for uploaded files.
; http://php.net/upload-max-filesize
upload_max_filesize = 2M
; Maximum number of files that can be uploaded via a single request
max_file_uploads = 20
此外還有：
; Maximum size of POST data that PHP will accept.
; Its value may be 0 to disable the limit. It is ignored if POST data reading
; is disabled through enable_post_data_reading.
; http://php.net/post-max-size
post_max_size = 8M
; Maximum amount of memory a script may consume (128MB)
; http://php.net/memory-limit
memory_limit = 128M
; Maximum execution time of each script, in seconds
; http://php.net/max-execution-time
; Note: This directive is hardcoded to 0 for the CLI SAPI
max_execution_time = 30
; Maximum amount of time each script may spend parsing request data. It's a good
; idea to limit this time on productions servers in order to eliminate unexpectedly
; long running scripts.
; Note: This directive is hardcoded to -1 for the CLI SAPI
; Default Value: -1 (Unlimited)
; Development Value: 60 (60 seconds)
; Production Value: 60 (60 seconds)
; http://php.net/max-input-time
max_input_time = 60
