To enable transformations, you have to setup the column_info table and the proper directives. Please see the :ref:`config` on how to do so.
You can apply different transformations to the contents of each column. The transformation will take the content of each column and transform it with certain rules defined in the selected transformation.
Say you have a column 'filename' which contains a filename. Normally you would see in phpMyAdmin only this filename. Using 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 consult your <www.your-host.com>/<your-install- dir>/transformation_overview.php installation.
For a tutorial on how to effectively use transformations, see our Link section on the official phpMyAdmin homepage.
Go to your tbl_structure.php page (i.e. reached through clicking on the 'Structure' link for a table). There click on "Change" (or change icon) and there you will see three new fields at the end of the line. They are called 'MIME-type', 'Browser transformation' and 'Transformation options'.
- The field 'MIME-type' is a drop-down field. Select the MIME-type that corresponds to the column's contents. Please note that transformations are inactive as long as no MIME-type is selected.
- The field 'Browser 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 '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'".
All specific transformations for mimetypes are defined through class files in the directory 'libraries/plugins/transformations/'. Each of them extends a certain transformation abstract class declared in libraries/plugins/transformations/abstract.
They are stored in files to ease up customization and easy adding of new transformations.
Because the user cannot enter own mimetypes, it is kept sure that transformations 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 'transformations.lib.php' that provides some basic functions which can be included by any other transform function.
The file name convention is [Mimetype]_[Subtype]_[Transformation Name].class.php, while the abtract 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 libraries/plugins/transformations/TEMPLATE and libraries/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:`libraries/plugins/transformations/generator_plugin.sh` or :file:`libraries/plugins/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() function. This means, all object properties described on the manual page 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 MIME-type of the column (i.e. 'text/plain', 'image/jpeg' etc.)