PHP Manual: String Filters

String Filters

Each of these filters does precisely what their name implies and correspond to the behavior of a built-in php string handling function. For more information on a given filter, refer to the manual page for the corresponding function.

string.rot13

Use of this filter is equivalent to processing all stream data through the str_rot13 function.

Example #1 string.rot13

<?php
$fp = fopen('php://output', 'w');
stream_filter_append($fp, 'string.rot13');
fwrite($fp, "This is a test.\n");
/* Outputs:  Guvf vf n grfg.   */
?>

string.toupper

Use of this filter is equivalent to processing all stream data through the strtoupper function.

Example #2 string.toupper

<?php
$fp = fopen('php://output', 'w');
stream_filter_append($fp, 'string.toupper');
fwrite($fp, "This is a test.\n");
/* Outputs:  THIS IS A TEST.   */
?>

string.tolower

Use of this filter is equivalent to processing all stream data through the strtolower function.

Example #3 string.tolower

<?php
$fp = fopen('php://output', 'w');
stream_filter_append($fp, 'string.tolower');
fwrite($fp, "This is a test.\n");
/* Outputs:  this is a test.   */
?>

string.strip_tags

Use of this filter is equivalent to processing all stream data through the strip_tags function. It accepts parameters in one of two forms: Either as a string containing a list of tags similar to the second parameter of the strip_tags function, or as an array of tag names.

Warning

This feature has been DEPRECATED as of PHP 7.3.0. Relying on this feature is highly discouraged.

Example #4 string.strip_tags

<?php
$fp = fopen('php://output', 'w');
stream_filter_append($fp, 'string.strip_tags', STREAM_FILTER_WRITE, "<b><i><u>");
fwrite($fp, "<b>bolded text</b> enlarged to a <h1>level 1 heading</h1>\n");
fclose($fp);
/* Outputs:  bolded text enlarged to a level 1 heading   */

$fp = fopen('php://output', 'w');
stream_filter_append($fp, 'string.strip_tags', STREAM_FILTER_WRITE, array('b','i','u'));
fwrite($fp, "<b>bolded text</b> enlarged to a <h1>level 1 heading</h1>\n");
fclose($fp);
/* Outputs:  bolded text enlarged to a level 1 heading   */
?>