repo_zf1/documentation/manual/en/tutorials/autoloading-intro.xml

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<sect1 id="learning.autoloading.intro">
    <title>Introduction</title>

    <para>
        Autoloading is a mechanism that eliminates the need to manually require dependencies within
        your <acronym>PHP</acronym> code. Per <ulink url="http://php.net/autoload">the PHP
        autoload manual</ulink>, once an autoloader has been defined, it "is automatically called
        in case you are trying to use a class or an interface which hasn't been defined yet."
    </para>

    <para>
        Using autoloading, you do not need to worry about <emphasis>where</emphasis> a class exists
        in your project. With well-defined autoloaders, you do not need to worry about where a class
        file is relative to the current class file; you simply use the class, and the autoloader
        will perform the file lookup.
    </para>

    <para>
        Additionally, autoloading, because it defers loading to the last possible moment and ensures
        that a match only has to occur once, can be a huge performance boost -- particularly if you
        take the time to strip out <methodname>require_once()</methodname> calls before you move
        to deployment.
    </para>

    <para>
        Zend Framework encourages the use of autoloading, and provides several tools to provide
        autoloading of both library code as well as application code. This tutorial covers these
        tools, as well as how to use them effectively.
    </para>
</sect1>