ob_get_contents()

(PHP 4, PHP 5, PHP 7)

返回输出缓冲区的内容

说明

只是得到输出缓冲区的内容，但不清除它。

返回值

此函数返回输出缓冲区的内容，或者如果输出缓冲区无效将返回FALSE。

范例

A simpleob_get_contents()example

以上例程会输出：

string(6) "Hello "
string(11) "Hello World"

参见

• ob_start() 打开输出控制缓冲
• ob_get_length() 返回输出缓冲区内容的长度

This is an example of how the stack works: 

Note that, unlike PHP variables which make efficient use of memory, getting the contents of the output buffer results in a new copy of the buffer being made. This can end up massively increasing the memory requirements of your script if your output is large.
Example code:

Output:
 351664
 5359152
10359256

The ob_get_contents() function has different return behaivor in PHP 5.3.x and PHP 5.5.x. Take a look at very simple example for PHP 5.3

Output: bool(false) 
but in PHP 5.5.x, the same php code will return: 
Output: string (0) "" 
Actually, we can use type regulation - intval(ob_get_contents()), for cheking On/Off output buffering, but it lays the possible problems in the future.

i made a simple test which is faster: adding some text in the normal way or by the ob stack:

Outputs something like this:
0.33658003807068
0.30778789520264

if you use ob_start with a callback function as a parameter, and that function changes ob string (as in example in manual) don't expect that ob_get_contents will return changed ob.
it will work as you would use ob_start with no parameter at all. So don't be confused.

transfer image, another method (alternative to fsockopen or function socket) :
server(192.168.0.1)
makeimage.php
    ...........
    ...........
    $nameimage="xxxx.jpg"
    $comand=exec("plotvelocity.sh $nameimage $paramater1 $paramater2");
    ob_start();
    readfile($nameimage);
    $image_data = ob_get_contents();
    ob_end_clean();
    echo $image_data;
    unlink($nameimage);
Client (192.168.0.2)
 $bild="images/newimage2.gif";
 $host="192.168.0.1";
 $url=file_get_contents("http://$host/makeimage.php?$querystring");
 $fp = fopen("$bild", 'wb');
 fwrite($fp, $url);
 fclose($fp);
 echo '';
naturally you can transfer whichever thing and not only images

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