fflush()

(PHP 4 >= 4.0.1, PHP 5, PHP 7)

将缓冲内容输出到文件

说明

本函数强制将所有缓冲的输出写入$handle文件句柄所指向的资源。成功时返回TRUE，或者在失败时返回FALSE。

文件指针必须是有效的，必须指向由fopen()或fsockopen()成功打开的文件(并还未由fclose()关闭)。

参数

文件指针必须是有效的，必须指向由fopen()或fsockopen()成功打开的文件(并还未由fclose()关闭)。

返回值

成功时返回TRUE，或者在失败时返回FALSE。

范例

File write example usingfflush()

参见

• clearstatcache() 清除文件状态缓存
• fwrite() 写入文件（可安全用于二进制文件）

A hint for PHP beginners like me:
The buffered output which is write by fflush() has nothing to do with the output buffer which is initiated by the ob_start() function.

Sorry, the note I previously added regarding fflush() has a bug!
when you read file by calling 
$fp = fopen("myfile", "a+");
and you wish to read the content, you have to call 
rewind($fp) before you attemp to read it. (Silly me) Or else if you tried something like
$fp = fopen("myfile", "a+");
$content = fread($fp);
// show that content is in fact null
if ($content == NULL)
 print "but it must be first put to rewind
\n";
will result
but it must be first put to rewind.
[new line]
in fact, if you are not careful (like me), and you opened it with
$fp = fopen("myfile", "r+");
$content = fread($fp);
..
// do something with content
..
then you tried to again
$content = fread($fp);
without rewind, you'd get NULL again. This sounds trivial, but if you work with several file resources, with freads and fopens everywhere, you can get easily lost. So becareful.

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