Migrate text field with multiple values I've got a simple Text field which allows 2 values, let's call it field_text. My source database has two columns, let's say text1 and text2. 

I want to set my migrate field mapping so that text1 is used as the first value for field_text and use text2 as the second value for field_text.

In other words, something like this:

$this-&gt;addFieldMapping('field_text[0]', 'text1');
$this-&gt;addFieldMapping('field_text[1]', 'text2');
You should implement prepareRow() method in your migration class. Inside prepareRow() you can read both source fields and add them to an array.
I will provide an example:

public function prepareRow($row) {
  $row-&gt;text1 = array($row-&gt;text1, $row-&gt;text2);
}


Now your source field "text1" will contain both values and it can be mapped to "field_text". "text2" has to be set to DNM (do not map).