Sort array into unique strings and display results..

Overview: Sort unique string from an array and display results into a variable which can be echoed into jQuery to be displayed as a graph.

I using Wordpress with a repeater from custom post fields plugin, code below:

$repeater = get_field('treatments');

foreach( $repeater as $key => $row ) {
    column_id[ $key ] = $row['treatment_name'];
  }

array_multisort( $column_id, SORT_ASC, $repeater );

foreach( $repeater as $row ) {
    print_r($row);
}

The print_r returns..

Array ( [treatment_name] => back pain [pain_level] => 4 )
Array ( [treatment_name] => back pain [pain_level] => 5 ) 
Array ( [treatment_name] => back pain [pain_level] => 7 ) 
Array ( [treatment_name] => back pain [pain_level] => 10 ) 
Array ( [treatment_name] => shoulder pain [pain_level] => 3 ) 
Array ( [treatment_name] => shoulder pain [pain_level] => 8 ) 
Array ( [treatment_name] => shoulder pain [pain_level] => 10 )

I wish to be able to sort the array data into a variable I can using within JS.

{ treatment: '1', a: 4, b: 3 },
{ treatment: '2', a: 5, b: 8 },
{ treatment: '3', a: 7, b: 10 },
{ treatment: '4', b: 10 },

A = back pain B = shoulder pain

[treatment_name] - is a text field, so I looking for every unique [treatment_name] to added for example having one treatment called 'foot ache' with the pain level of 6 would be added to the start of the list as C.

e.g.

{ treatment: '1', a: 4, b: 3, c: 6 },
{ treatment: '2', a: 5, b: 8 },
{ treatment: '3', a: 7, b: 10 },
{ treatment: '4', b: 10 },

I have gone over and over trying to work the logic out but seems my level of php is not up to par, so I thought no better place to asked then the people who got me this far..

Any questions please do let me know, and anyone will to help your a star..