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List Form Field

The list form field type provides a drop down list or a list box of custom-defined entries. If the field has a saved value this is selected when the page is first loaded. If not, the default value (if any) is selected.

  • type (mandatory) must be list.
  • name (mandatory) is the unique name of the field.
  • label (mandatory) (translatable) is the field html label.
  • description (optional) (translatable) is the field description.
  • class (optional) is a CSS class name for the HTML form field. If omitted this will default to 'inputbox'.
  • multiple (optional) if set to true allows multiple items to be selected at the same time. Set to false to allow single selection.
  • required (optional) if set to true, the first field option should be empty, see last example.
  • useglobal (optional) if set to true, it will show the value that is set in the global configuration if found in the database.

Implemented by: libraries/src/Form/Field/ListField.php

The XML <field> element must include one or more <option> elements which define the list items. The text between the <option> and </option> tags is what will be shown in the drop down list and is a translatable string. The <option> tag takes the following argument:

  • value (mandatory) is the value that will be saved for the field if this item is selected.
  • requires (optional) Values: multilanguage, associations and adminlanguage can be used.

Tip: Don't forget to close the field definition with </field>.

Tip: Add first an option without a value, with a text like "Select an option". Otherwise, in case of a required field, the first option with a value gets silently selected (i.e., without the user choosing it). This text will typically be seen by users before clicking the dropdown list.

Tip: Some values for "name" field are reserved, so don't use them and avoid problems. One of them is: "style".

The response will be a numeric array with the elements being the values of the options selected. Options which are not selected will not be present in the array.

Example XML parameter definition

<field
        name="mylistvalue" 
        type="list" 
        default="" 
        label="Select an option" 
        description="">
        <option value="">Please Select</option>
        <option value="0">Option 1</option>
        <option value="1">Option 2</option>
</field>

Example XML parameter definition with required value

<field
        name="mylistvalue" 
        type="list" 
        default="" 
        required="true" 
        label="Select an option" 
        description="">
        <option value="">Please Select</option>
        <option value="0">Option 1</option>
        <option value="1">Option 2</option>
</field>

Showon attribute for list options

Since Joomla 3.9.0 one can use the showon attribute for option tags in a list field.

This feature was introduced with the Pull Request #18998.

Example XML parameter definition with showon

This is the definition for two list fields fielda and fieldb where the displayed options of fieldb are controlled by selections in fielda

<field
    name="fielda"
    type="list"
    label="FIELDA_LABEL"
    description="FIELDA_DESC"
    >
    <option value="editor">TYPE_EDITOR</option>
    <option value="text">TYPE_TEXT</option>
    <option value="textarea">TYPE_TEXTAREA</option>
</field>

<field
    name="fieldb"
    type="list"
    label="FIELDB_LABEL"
    description="FIELDB_DESC"
    >
    <option value="0">JNO</option>
    <option value="1">Option 1</option>
    <option
	    showon="fielda:text,textarea"
	    value="2">Option 2</option>
    <option
	    showon="fielda:text"
	    value="3">Option 3</option>
</field>
  • "Option 3" of fieldb is only displayed if option "TYPE_TEXT" is selected in fielda.
  • "Option 2" of fieldb is only displayed if option "TYPE_TEXT" OR "TYPE_TEXTAREA" is selected in fielda.
  • "Option 1" and "JNO" of fieldb is always displayed.

See also