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.
(PHP 4 >= 4.0.1, PHP 5, PHP 7, PHP 8)
fflush — 将缓冲内容输出到文件
$handle
) : bool
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)。
成功时返回 true， 或者在失败时返回 false。
Example #1 File write example using fflush()
<?php
$filename = 'bar.txt';
$file = fopen($filename, 'r+');
rewind($file);
fwrite($file, 'Foo');
fflush($file);
ftruncate($file, ftell($file));
fclose($file);
?>
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<br>\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.