Si hubo error al plantear la pregunta, no es input es textarea.
Código PHP:
<?php
$ThisFileName = "TextArea.php";
$ValueField = $_POST['ValueField'];
$SinSalto = $ValueField;
$ConSalto = str_replace("\n", "<br>", $ValueField);
print("</form><P>\n");
print("<form action=\"$ThisFileName\" method=post>");
print("<textarea name=ValueField type= textarea cols=100 rows=3>$ValueField</textarea>");
print("$SinSalto<P>");
print("$ConSalto<P>");
print("<input type=submit name=TextArea value=\"TextArea\"> <P>\n");
print("</form><P>\n");
$MyFile = "/home/Compartido/TextArea.php.txt";
$MyFileHand = fopen($MyFile, "w");
fwrite($MyFileHand, "SinSalto\n$SinSalto\n");
fwrite($MyFileHand, "ConSalto\n$ConSalto\n");
fclose($MyFileHand);
?>