Prueba esto y cuentanos que tal te funciona
Código PHP:
<html>
<head>
<title>New document</title>
<script type="text/javascript">
function ResizeTextArea(txtBox) {
nCols = txtBox.cols;
sVal = txtBox.value;
nVal = sVal.length;
nRowCnt = 1;
for (i=0;i<nVal;i++) {
if (sVal.charAt(i).charCodeAt(0) == 13) {
nRowCnt +=1;
}
}
if (nRowCnt < (nVal / nCols)) {
nRowCnt = 1 + (nVal / nCols);
}
txtBox.rows = nRowCnt;
}
</script>
</head>
<body>
<form name=frmSubmit method=post >
<textarea
name=txtTest
cols=50
rows=1
style='overflow:hidden'
onkeypress="ResizeTextArea(this);">
</textarea>
</form>
</body>
</html>