Php/docs/filters.string
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. */?>