<?php
$words = [
    'bailey', 'boffey', 'böhm', 'brown', 'серге́й', 'сергий', 'swag', 'svere'
];

$collator = new Collator( 'sv@collation=standard' );
foreach ( $words as $word )
{
    $sortKey = $collator->getSortKey( $word );
    printf("%-26s: %-12s\n", bin2hex( $sortKey ), $word );
}
?>
Output
2d2b3b41335b010a010a : bailey 2d473535335b010a010a : boffey 2d5e7704394301080108 : böhm 2d4d47574501090109 : brown 629c289610284e01418805010b: серге́й 629c289610464e010a010a : сергий 4f572b3701080108 : swag 4f55334d3301090109 : svere