ContextQMD
Back to Phpmyadmin

Transformations

docs/transformations.rst

4.5.0.17.7 KB
Original Source

.. _transformations:

Transformations

.. note::

You need to have configured the :ref:`linked-tables` to use the transformations
feature.

.. _transformationsintro:

Introduction ++++++++++++

To enable transformations, you have to set up the column_info table and the proper directives. Please see the :ref:config on how to do so.

phpMyAdmin has two different types of transformations: browser display transformations, which affect only how the data is shown when browsing through phpMyAdmin; and input transformations, which affect a value prior to being inserted through phpMyAdmin. You can apply different transformations to the contents of each column. Each transformation has options to define how it will affect the stored data.

Say you have a column filename which contains a filename. Normally you would see in phpMyAdmin only this filename. Using display transformations you can transform that filename into a HTML link, so you can click inside of the phpMyAdmin structure on the column's link and will see the file displayed in a new browser window. Using transformation options you can also specify strings to append/prepend to a string or the format you want the output stored in.

For a general overview of all available transformations and their options, you can either go to the Change link for an existing column or from the dialog to create a new column, in either case there is a link on that column structure page for "Browser display transformation" and "Input transformation" which will show more information about each transformation that is available on your system.

For a tutorial on how to effectively use transformations, see our Link section <https://www.phpmyadmin.net/docs/>_ on the official phpMyAdmin homepage.

.. _transformationshowto:

Usage +++++

Go to the table structure page (reached by clicking on the 'Structure' link for a table). There click on "Change" (or the change icon) and there you will see the five transformation--related fields at the end of the line. They are called ':term:Media type', 'Browser transformation' and 'Transformation options'.

  • The field ':term:Media type' is a drop-down field. Select the :term:Media type that corresponds to the column's contents. Please note that many transformations are inactive until a :term:Media type is selected.
  • The field 'Browser display transformation' is a drop-down field. You can choose from a hopefully growing amount of pre-defined transformations. See below for information on how to build your own transformation. There are global transformations and mimetype-bound transformations. Global transformations can be used for any mimetype. They will take the mimetype, if necessary, into regard. Mimetype-bound transformations usually only operate on a certain mimetype. There are transformations which operate on the main mimetype (like 'image'), which will most likely take the subtype into regard, and those who only operate on a specific subtype (like 'image/jpeg'). You can use transformations on mimetypes for which the function was not defined for. There is no security check for you selected the right transformation, so take care of what the output will be like.
  • The field 'Browser display transformation options' is a free-type textfield. You have to enter transform-function specific options here. Usually the transforms can operate with default options, but it is generally a good idea to look up the overview to see which options are necessary. Much like the ENUM/SET-Fields, you have to split up several options using the format 'a','b','c',...(NOTE THE MISSING BLANKS). This is because internally the options will be parsed as an array, leaving the first value the first element in the array, and so forth. If you want to specify a MIME character set you can define it in the transformation_options. You have to put that outside of the pre- defined options of the specific mime-transform, as the last value of the set. Use the format "'; charset=XXX'". If you use a transform, for which you can specify 2 options and you want to append a character set, enter "'first parameter','second parameter','charset=us-ascii'". You can, however use the defaults for the parameters: "'','','charset =us-ascii'". The default options can be configured using :config:option:$cfg['DefaultTransformations'].
  • 'Input transformation' is another drop-down menu that corresponds exactly with the instructions above for "Browser display transformation" except these these affect the data before insertion in to the database. These are most commonly used to either provide a specialized editor (for example, using the phpMyAdmin SQL editor interface) or selector (such as for uploading an image). It's also possible to manipulate the data such as converting an IPv4 address to binary or parsing it through a regular expression.
  • Finally, 'Input transformation options' is the equivalent of the "Browser display transformation options" section above and is where optional and required parameters are entered.

.. _transformationsfiles:

File structure ++++++++++++++

All specific transformations for mimetypes are defined through class files in the directory :file:src/Plugins/Transformations/. Each of them extends a certain transformation abstract class declared in :file:src/Plugins/Transformations/Abs.

They are stored in files to ease customization and to allow easy adding of new or custom transformations.

Because the user cannot enter their own mimetypes, it is kept certain that the transformations will always work. It makes no sense to apply a transformation to a mimetype the transform-function doesn't know to handle.

There is a file called :file:src/Plugins/Transformations.php that provides some basic functions which can be included by any other transform function.

The file name convention is [Mimetype]_[Subtype]_[Transformation Name].php, while the abstract class that it extends has the name [Transformation Name]TransformationsPlugin. All of the methods that have to be implemented by a transformations plug-in are:

#. getMIMEType() and getMIMESubtype() in the main class; #. getName(), getInfo() and applyTransformation() in the abstract class it extends.

The getMIMEType(), getMIMESubtype() and getName() methods return the name of the MIME type, MIME Subtype and transformation accordingly. getInfo() returns the transformation's description and possible options it may receive and applyTransformation() is the method that does the actual work of the transformation plug-in.

Please see the :file:src/Plugins/Transformations/TEMPLATE and :file:src/Plugins/Transformations/TEMPLATE\_ABSTRACT files for adding your own transformation plug-in. You can also generate a new transformation plug-in (with or without the abstract transformation class), by using :file:bin/transformations_generator_plugin.sh or :file:bin/transformations_generator_main_class.sh.

The applyTransformation() method always gets passed three variables:

#. $buffer - Contains the text inside of the column. This is the text, you want to transform. #. $options - Contains any user-passed options to a transform function as an array. #. $meta - Contains an object with information about your column. The data is drawn from the output of the mysql\_fetch\_field() <https://www.php.net/mysql_fetch_field>_ function. This means, all object properties described on the manual page <https://www.php.net/mysql_fetch_field>_ are available in this variable and can be used to transform a column accordingly to unsigned/zerofill/not_null/... properties. The $meta->mimetype variable contains the original :term:Media type of the column (i.e. 'text/plain', 'image/jpeg' etc.)