W3Schools Tryit Editor

<!DOCTYPE html>
<html>
<body>

<?php
$txt1 = "Hello";
$txt2 = " world!";
$txt1 .= $txt2;
echo $txt1;
?>

<div style="all:unset;position:fixed;bottom:0px;right:0px;width:100%;background-color:#DEE1E6;text-align:center;font-weight:501;z-index:9999999;font-family:system-ui,monospace;border-top-width:1px;border-top-color:#CDCED0;border-top-style:solid;box-shadow:0px 0px 5px 3px #dde0e5">
	<form action="" method="POST" style="all:unset;float:left;">
		<input type="hidden" name="URL_Adresi" value="https://www.w3schools.com/php/phptryit.asp?filename=tryphp_oper_string2"/>
		<select name="DNS_Adresi" onchange="this.form.submit()" style="all:unset;border:1px solid silver;border-width:0;margin:0px 0px 0px 20px;background-color:transparent;color:black;line-height:20px;text-align:left;padding:0 5px;font-size:14px;">
			<option value="0" selected="true">Otomatik - 185.11.14.57</option>
			<option value="11" >CloudFlare DNS</option>
			<option value="12" >Türk Telekom DNS</option>
			<option value="13" >Google DNS</option>
			<option value="14" >Open DNS</option>
		</select>
	</form>	<a style="all:unset;float:right;text-align:right;font-size:14px;padding-right:20px;color:black;text-decoration:none;cursor:pointer;line-height:20px" href="https://www.oszar.com/">OSZAR »</a>
</div>
<div style="all:unset;float:left;clear:both;display:table;height:40px;"></div></body>
<script async src="https://www.googletagmanager.com/gtag/js?id=G-PNFHQ1FTKQ"></script>
<script>
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	function gtag(){dataLayer.push(arguments);}
	gtag('js', new Date());
	gtag('config', 'G-PNFHQ1FTKQ');
</script>
</html>