PHP : Function Reference : Stream Functions : stream_filter_append PHP Examples Tutorials References

Example 2374. Controlling where filters are applied

<?php
/* Open a test file for reading and writing */
$fp = fopen('test.txt', 'w+');

/* Apply the ROT13 filter to the

 * write filter chain, but not the

 * read filter chain */
stream_filter_append($fp, "string.rot13", STREAM_FILTER_WRITE);

/* Write a simple string to the file

 * it will be ROT13 transformed on the

 * way out */
fwrite($fp, "This is a test\n");

/* Back up to the beginning of the file */
rewind($fp);

/* Read the contents of the file back out.

 * Had the filter been applied to the

 * read filter chain as well, we would see

 * the text ROT13ed back to its original state */
fpassthru($fp);

fclose($fp);

/* Expected Output

   ---------------


Guvf vf n grfg


 */
?>

Hello firends The difference betweem adding a stream filter first or last in the filte list in only the order they will be applied to streams. For example, if you're reading data from a file, and a given filter is placed in first place with stream_filter_prepend()the data will be processed by that filter first. This example reads out file data and the filter is applied at the beginning of the reading operation: <?php /* Open a test file for reading */ $fp = fopen("test.txt", "r"); /* Apply the ROT13 filter to the * read filter chain, but not the * write filter chain */ stream_filter_prepend($fp, "string.rot13", STREAM_FILTER_READ); // read file data $contents=fread($fp,1024); // file data is first filtered and stored in $contents echo $contents; fclose($fp); ?> On the other hand, if stream_filter_append() is used, then the filter will be applied at the end of the data operation. The thing about this is only the order filters are applied to streams. Back to the example, it's not the same thing removing new lines from file data and then counting the number of characters, than performing the inverse process. In this case, the order that filters are applied to stream is important. This example writes a test string to a file. The filter is applied at the end of the writing operation: <?php /* Open a test file for writing */ $fp = fopen("test.txt", "w+"); /* Apply the ROT13 filter to the * write filter chain, but not the * read filter chain */ stream_filter_append($fp, "string.rot13", STREAM_FILTER_WRITE); /* Write a simple string to the file * it will be ROT13 transformed at the end of the stream operation * way out */ fwrite($fp, "This is a test\n"); // string data is first written, then ROT13 tranformed and lastly written to file /* Back up to the beginning of the file */ rewind($fp); $contents=fread($fp,512); fclose($fp); echo $contents; ?> In the first case, data is transformed at the end of the writing operation, while in the second one, data is first filtered and then stored in $contents. With Regards Hossein

stream_filter_append

Attach a filter to a stream (PHP 4 >= 4.3.0, PHP 5)
resource stream_filter_append ( resource stream, string filtername [, int read_write [, mixed params]] )

Example 2374. Controlling where filters are applied

Related Examples ( Source code ) » stream_filter_append

Code Examples / Notes » stream_filter_append

Change Language

stream_filter_append

Attach a filter to a stream (PHP 4 >= 4.3.0, PHP 5) resource stream_filter_append ( resource stream, string filtername [, int read_write [, mixed params]] )

Example 2374. Controlling where filters are applied

Related Examples ( Source code ) » stream_filter_append

Code Examples / Notes » stream_filter_append

Change Language

Attach a filter to a stream (PHP 4 >= 4.3.0, PHP 5)
resource stream_filter_append ( resource stream, string filtername [, int read_write [, mixed params]] )