If one element in the php-PHP array is the same, splice other elements.

For example, the original array is an array (3) {[0] & gt; array (6) {[& quot; pla_id & quot;] & gt; string (3) & quot; 298 & quot; [& quot; user_id & quot;] & gt; string (1) & quot; 1 & quot; [& quot; due_in & quot;] & gt; string (15) & quot; 8.33 & quot;} [1] & gt; array (6) {[& quot; pla_id & quot;] & gt php

For example, the original array is like this.
Array (3 ){
[0] => array (6 ){
["Pla_id"] => string (3) "298"
["User_id"] => string (1) "1"
["Due_in"] => string (15) "8.33"
}
[1] => array (6 ){
["Pla_id"] => string (3) "976"
["User_id"] => string (1) "1"
["Due_in"] => string (15) "338.90"
}
[2] => array (6 ){
["Pla_id"] => string (3) "56"
["User_id"] => string (1) "2"
["Due_in"] => string (15) "25.6"
}}

Because the user_id = 1 in the array is the same
To get the final array like this, how do I write (that is, concatenate other elements with the same user_id )?
Array (3 ){
[0] => array (6 ){
["Pla_id"] => string (3) "298,976"
["User_id"] => string (1) "1"
["Due_in"] => string (15) "8.33, 338.90"
}

[1] => array (6 ){
["Pla_id"] => string (3) "56"
["User_id"] => string (1) "2"
["Due_in"] => string (15) "25.6"
}}