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    Magic constants

    PHP provides a large number of predefined constants to any script which it runs. Many of these constants, however, are created by various extensions, and will only be present when those extensions are available, either via dynamic loading or because they have been compiled in.

    There are nine magical constants that change depending on where they are used. For example, the value of __LINE__ depends on the line that it's used on in your script. All these "magical" constants are resolved at compile time, unlike regular constants, which are resolved at runtime. These special constants are case-insensitive and are as follows:

    PHP's magic constants
    Denumire Descriere
    __LINE__ The current line number of the file.
    __FILE__ The full path and filename of the file with symlinks resolved. If used inside an include, the name of the included file is returned.
    __DIR__ The directory of the file. If used inside an include, the directory of the included file is returned. This is equivalent to dirname(__FILE__). This directory name does not have a trailing slash unless it is the root directory.
    __FUNCTION__ The function name, or {closure} for anonymous functions.
    __CLASS__ The class name. The class name includes the namespace it was declared in (e.g. Foo\Bar). When used in a trait method, __CLASS__ is the name of the class the trait is used in.
    __TRAIT__ The trait name. The trait name includes the namespace it was declared in (e.g. Foo\Bar).
    __METHOD__ The class method name.
    __NAMESPACE__ The name of the current namespace.
    ClassName::class The fully qualified class name.

    A se vedea și

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    User Contributed Notes 5 notes

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    291
    vijaykoul_007 at rediffmail dot com
    18 years ago
    the difference between
    __FUNCTION__ and __METHOD__ as in PHP 5.0.4 is that

    __FUNCTION__ returns only the name of the function

    while as __METHOD__ returns the name of the class alongwith the name of the function

    class trick
    {
          function doit()
          {
                    echo __FUNCTION__;
          }
          function doitagain()
          {
                    echo __METHOD__;
          }
    }
    $obj=new trick();
    $obj->doit();
    output will be ----  doit
    $obj->doitagain();
    output will be ----- trick::doitagain
    up
    47
    Tomek Perlak [tomekperlak at tlen pl]
    17 years ago
    The __CLASS__ magic constant nicely complements the get_class() function.

    Sometimes you need to know both:
    - name of the inherited class
    - name of the class actually executed

    Here's an example that shows the possible solution:

    <?php

    class base_class
    {
        function     say_a()
        {
            echo     "'a' - said the " . __CLASS__ . "<br/>";
        }

        function     say_b()
        {
            echo     "'b' - said the " . get_class($this) . "<br/>";
        }

    }

    class     derived_class extends base_class
    {
        function     say_a()
        {
                parent::say_a();
            echo     "'a' - said the " . __CLASS__ . "<br/>";
        }

        function     say_b()
        {
                parent::say_b();
            echo     "'b' - said the " . get_class($this) . "<br/>";
        }
    }

    $obj_b = new derived_class();

    $obj_b->say_a();
    echo     "<br/>";
    $obj_b->say_b();

    ?>

    The output should look roughly like this:

    'a' - said the base_class
    'a' - said the derived_class

    'b' - said the derived_class
    'b' - said the derived_class
    up
    10
    php at kenman dot net
    10 years ago
    Just learned an interesting tidbit regarding __FILE__ and the newer __DIR__ with respect to code run from a network share: the constants will return the *share* path when executed from the context of the share.

    Examples:

    // normal context
    // called as "php -f c:\test.php"
    __DIR__ === 'c:\';
    __FILE__ === 'c:\test.php';

    // network share context
    // called as "php -f \\computerName\c$\test.php"
    __DIR__ === '\\computerName\c$';
    __FILE__ === '\\computerName\c$\test.php';

    NOTE: realpath('.') always seems to return an actual filesystem path regardless of the execution context.
    up
    6
    Sbastien Fauvel
    8 years ago
    Note a small inconsistency when using __CLASS__ and __METHOD__ in traits (stand php 7.0.4): While __CLASS__ is working as advertized and returns dynamically the name of the class the trait is being used in, __METHOD__ will actually prepend the trait name instead of the class name!
    up
    0
    public at taliesinnuin dot net
    3 years ago
    If you're using PHP with fpm (common in this day and age), be aware that __DIR__ and __FILE__ will return values based on the fpm root which MAY differ from its actual location on the file system.

    This can cause temporary head-scratching if deploying an app where php files within the web root pull in PHP files from outside of itself (a very common case). You may be wondering why __DIR__ returns "/" when the file itself lives in /var/www/html or whathaveyou.

    You might handle such a situation by having NGINX explicitly add the necessary part of the path in its fastcgi request and then you can set the root on the FPM process / server / container to be something other than the webroot (so long as no other way it could become publicly accessible).

    Hope that saves someone five minutes who's moving code to FPM that uses __DIR__.
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