为何crontab -e不能执行fwrite写入文件？蹦溃了

function Write_FileFun_new($filename,$filedir, $htmldata = '') {<br />
	if(!is_dir($filedir)) {<br />
		mkdir($filedir, 0777);<br />
	}<br />
	$htmlfile = $filedir.$filename;<br />
	if($fp = fopen($htmlfile, 'wbt')) {<br />
		fwrite($fp,$htmldata);<br />
		fclose($fp);<br />
	} else {<br />
		echo "<center><p>can not write to files, please check directory $htmldir.</p>
                    <div class="aritcle_card">
                        <a class="aritcle_card_img" href="/ai/757">
                            <img src="https://img.php.cn/upload/ai_manual/001/503/042/68b6db8d245b8850.png" alt="Akkio">
                        </a>
                        <div class="aritcle_card_info">
                            <a href="/ai/757">Akkio</a>
                            <p>Akkio 是一个无代码 AI 的全包平台，任何人都可以在几分钟内构建和部署AI</p>
                            <div class="">
                                <img src="/static/images/card_xiazai.png" alt="Akkio">
                                <span>157</span>
                            </div>
                        </div>
                        <a href="/ai/757" class="aritcle_card_btn">
                            <span>查看详情</span>
                            <img src="/static/images/cardxiayige-3.png" alt="Akkio">
                        </a>
                    </div>
                </center>";<br />
		exit;<br />
	}<br />
}<br />
$testnum_temp="<?php \$testnum = ".(intval($testnum)+1)."; ?>";<br />
Write_FileFun_new("test.php","inc/", $testnum_temp);