139 lines
6.3 KiB
Plaintext
139 lines
6.3 KiB
Plaintext
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.. _transformations:
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Transformations
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===============
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.. _transformationsintro:
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Introduction
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++++++++++++
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To enable transformations, you have to setup the ``column_info``
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table and the proper directives. Please see the :ref:`config` on how to do so.
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You can apply different transformations to the contents of each
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column. The transformation will take the content of each column and
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transform it with certain rules defined in the selected
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transformation.
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Say you have a column 'filename' which contains a filename. Normally
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you would see in phpMyAdmin only this filename. Using transformations
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you can transform that filename into a HTML link, so you can click
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inside of the phpMyAdmin structure on the column's link and will see
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the file displayed in a new browser window. Using transformation
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options you can also specify strings to append/prepend to a string or
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the format you want the output stored in.
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For a general overview of all available transformations and their
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options, you can consult your *<www.your-host.com>/<your-install-
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dir>/transformation\_overview.php* installation.
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For a tutorial on how to effectively use transformations, see our
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`Link section <http://www.phpmyadmin.net/home_page/docs.php>`_ on the
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official phpMyAdmin homepage.
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.. _transformationshowto:
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Usage
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+++++
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Go to your *tbl\_structure.php* page (i.e. reached through clicking on
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the 'Structure' link for a table). There click on "Change" (or change
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icon) and there you will see three new fields at the end of the line.
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They are called 'MIME-type', 'Browser transformation' and
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'Transformation options'.
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* The field 'MIME-type' is a drop-down field. Select the MIME-type that
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corresponds to the column's contents. Please note that transformations
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are inactive as long as no MIME-type is selected.
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* The field 'Browser transformation' is a drop-down field. You can
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choose from a hopefully growing amount of pre-defined transformations.
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See below for information on how to build your own transformation.
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There are global transformations and mimetype-bound transformations.
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Global transformations can be used for any mimetype. They will take
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the mimetype, if necessary, into regard. Mimetype-bound
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transformations usually only operate on a certain mimetype. There are
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transformations which operate on the main mimetype (like 'image'),
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which will most likely take the subtype into regard, and those who
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only operate on a specific subtype (like 'image/jpeg'). You can use
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transformations on mimetypes for which the function was not defined
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for. There is no security check for you selected the right
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transformation, so take care of what the output will be like.
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* The field 'Transformation options' is a free-type textfield. You have
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to enter transform-function specific options here. Usually the
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transforms can operate with default options, but it is generally a
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good idea to look up the overview to see which options are necessary.
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Much like the ENUM/SET-Fields, you have to split up several options
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using the format 'a','b','c',...(NOTE THE MISSING BLANKS). This is
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because internally the options will be parsed as an array, leaving the
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first value the first element in the array, and so forth. If you want
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to specify a MIME character set you can define it in the
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transformation\_options. You have to put that outside of the pre-
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defined options of the specific mime-transform, as the last value of
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the set. Use the format "'; charset=XXX'". If you use a transform, for
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which you can specify 2 options and you want to append a character
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set, enter "'first parameter','second parameter','charset=us-ascii'".
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You can, however use the defaults for the parameters: "'','','charset
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=us-ascii'".
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.. _transformationsfiles:
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File structure
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++++++++++++++
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All specific transformations for mimetypes are defined through class
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files in the directory 'libraries/plugins/transformations/'. Each of
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them extends a certain transformation abstract class declared in
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libraries/plugins/transformations/abstract.
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They are stored in files to ease up customization and easy adding of
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new transformations.
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Because the user cannot enter own mimetypes, it is kept sure that
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transformations always work. It makes no sense to apply a
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transformation to a mimetype the transform-function doesn't know to
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handle.
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There is a file called '*transformations.lib.php*' that provides some
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basic functions which can be included by any other transform function.
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The file name convention is ``[Mimetype]_[Subtype]_[Transformation
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Name].class.php``, while the abtract class that it extends has the
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name ``[Transformation Name]TransformationsPlugin``. All of the
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methods that have to be implemented by a transformations plug-in are:
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#. getMIMEType() and getMIMESubtype() in the main class;
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#. getName(), getInfo() and applyTransformation() in the abstract class
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it extends.
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The getMIMEType(), getMIMESubtype() and getName() methods return the
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name of the MIME type, MIME Subtype and transformation accordingly.
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getInfo() returns the transformation's description and possible
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options it may receive and applyTransformation() is the method that
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does the actual work of the transformation plug-in.
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Please see the libraries/plugins/transformations/TEMPLATE and
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libraries/plugins/transformations/TEMPLATE\_ABSTRACT files for adding
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your own transformation plug-in. You can also generate a new
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transformation plug-in (with or without the abstract transformation
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class), by using
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:file:`libraries/plugins/transformations/generator_plugin.sh` or
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:file:`libraries/plugins/transformations/generator_main_class.sh`.
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The applyTransformation() method always gets passed three variables:
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#. **$buffer** - Contains the text inside of the column. This is the
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text, you want to transform.
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#. **$options** - Contains any user-passed options to a transform
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function as an array.
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#. **$meta** - Contains an object with information about your column. The
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data is drawn from the output of the `mysql\_fetch\_field()
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<http://www.php.net/mysql_fetch_field>`_ function. This means, all
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object properties described on the `manual page
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<http://www.php.net/mysql_fetch_field>`_ are available in this
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variable and can be used to transform a column accordingly to
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unsigned/zerofill/not\_null/... properties. The $meta->mimetype
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variable contains the original MIME-type of the column (i.e.
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'text/plain', 'image/jpeg' etc.)
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