PHP function returning reference conflicts with PHPCodeSniffer in custom WordPress plugin

Question

I tried the following code in my custom WordPress plugin:

function &test() {
  $a = 1;
  return $a;
}

This results in a codesniffer error:

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FOUND 1 ERROR AFFECTING 1 LINE
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 5 | ERROR | [x] No space after opening parenthesis is prohibited
   |       |     (WordPress.WhiteSpace.ControlStructureSpacing.NoSpaceAfterOpenParenthesis)
------------------------------------------------------------------------------------------------------------
PHPCBF CAN FIX THE 1 MARKED SNIFF VIOLATIONS AUTOMATICALLY
------------------------------------------------------------------------------------------------------------

How to fix? Show me working code, please.