workHour/app/Exports/ResearchProjectDetailMultiExport.php

<?php

namespace App\Exports;

use Maatwebsite\Excel\Concerns\WithMultipleSheets;

class ResearchProjectDetailMultiExport implements WithMultipleSheets
{
    protected $year;
    protected $projects;
    protected $taxInfo;

    public function __construct($year, array $projects, array $taxInfo) {
        $this->year = $year;
        $this->projects = $projects;
        $this->taxInfo = $taxInfo;
    }

    public function sheets(): array {
        $sheets = [];
        foreach ($this->projects as $project) {
            $sheets[] = new ResearchProjectDetailSheetExport($this->year, $project, $this->taxInfo);
        }
        return $sheets;
    }
}