<?php

class streamDownload
{
    public $flg = false;
    public $fileName = '';
    public $to_encoding = 'sjis';
    public $from_encoding = 'UTF-8';

    public function __construct($fileName,$to_encoding = 'sjis',$from_encoding = 'UTF-8')
    {
        $this->fileName = $fileName;
        return $this;
    }

    public function checkSplFileInfo()
    {
        if((new SplFileInfo($this->fileName))->getExtension() === 'csv'){
            $this->flg = true;
        }
        return $this;
    }

    public function download($data)
    {
        if(!$this->flg){
            return $this->flg;
        }

        header('Content-Type: application/octet-stream');
        header('Content-Disposition: attachment; filename='.$this->fileName);        
        $stream = fopen('php://output', 'w');
            foreach ($data as $row) {
                $row = mb_convert_encoding($row,$this->to_encoding,$this->from_encoding);
                fputcsv($stream, $row);
            }
        fclose($stream);
        exit;
    }
}

$data = [
    ['テスト1', '高知太郎', 'abc@example.com'],
    ['テスト2', '高知花子', 'def@example.com'],
    ['テスト3', '高知喜多郎', 'dev@example.com'],
];

(new streamDownload('test.csv'))->checkSplFileInfo()->download($data);

function sosu(){
    let sosuno = [2];
    for(let i=3;i<=9999;i++){
        let flg = true;
        if(i%2===0){
            continue;
        }
        for(let ii=2;ii<i;ii++){
            if(ii%2===0){
                continue;
            }
            if(i%ii===0){
                flg = false;
                break;
            }
        }
        if(flg){
            sosuno.push(i);
        }
    }
    document.getElementById("my-textarea").value = sosuno.join(',');
}
document.getElementById("btn").addEventListener("click",sosu);