How does php fwrite write multiple variables at the same time?

<?php
$name=":".$_POST["name"]."\r\n";
$tel=":".$_POST["tel"]."\r\n";
$auto=":".$_POST["auto"]."\r\n";
$fp=fopen("auto.txt","w");
fwrite($fp,$name);
fwrite($fp,$tel);
fwrite($fp,$auto);

how not to write fwrite? 3 times

Php
Mar.06,2021

fwrite($fp,$name.$tel.$auto);
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