List of Available Filters
Conversion Filters
List of Available Filters
PHP Manual

## 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 (since PHP 5.0.0) 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.

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: <b>bolded text</b> 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: <b>bolded text</b> enlarged to a level 1 heading */
?>`

List of Available Filters
Conversion Filters
List of Available Filters
PHP Manual