<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> <title>List of Available Filters</title> </head> <body><div class="manualnavbar" style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="resource.html">List of Resource Types</a></div> <div class="next" style="text-align: right; float: right;"><a href="filters.string.html">String Filters</a></div> <div class="up"><a href="appendices.html">Appendices</a></div> <div class="home"><a href="index.html">PHP Manual</a></div> </div><hr /><div id="filters" class="appendix"> <h1>List of Available Filters</h1> <h2>Table of Contents</h2><ul class="chunklist chunklist_appendix"><li><a href="filters.string.html">String Filters</a></li><li><a href="filters.convert.html">Conversion Filters</a></li><li><a href="filters.compression.html">Compression Filters</a></li><li><a href="filters.encryption.html">Encryption Filters</a></li></ul> <p class="para"> The following is a list of a few built-in stream filters for use with <span class="function"><a href="function.stream-filter-append.html" class="function">stream_filter_append()</a></span>. Your version of PHP may have more filters (or fewer) than those listed here. </p> <p class="para"> It is worth noting a slight asymmetry between <span class="function"><a href="function.stream-filter-append.html" class="function">stream_filter_append()</a></span> and <span class="function"><a href="function.stream-filter-prepend.html" class="function">stream_filter_prepend()</a></span>. Every PHP stream contains a small <em class="emphasis">read buffer</em> where it stores blocks of data retrieved from the filesystem or other resource in order to process data in the most efficient manner. As soon as data is pulled from the resource into the stream's internal buffer, it is immediately processed through any attached filters whether the PHP application is actually ready for the data or not. If data is sitting in the read buffer when a filter is <em class="emphasis">appended</em>, this data will be immediately processed through that filter making the fact that it was sitting in the buffer seem transparent. However, if data is sitting in the read buffer when a filter is <em class="emphasis">prepended</em>, this data will <em class="emphasis">NOT</em> be processed through that filter. It will instead wait until the next block of data is retrieved from the resource. </p> <p class="para"> For a list of filters installed in your version of PHP use <span class="function"><a href="function.stream-get-filters.html" class="function">stream_get_filters()</a></span>. </p> </div> <hr /><div class="manualnavbar" style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="resource.html">List of Resource Types</a></div> <div class="next" style="text-align: right; float: right;"><a href="filters.string.html">String Filters</a></div> <div class="up"><a href="appendices.html">Appendices</a></div> <div class="home"><a href="index.html">PHP Manual</a></div> </div></body></html>
