Norm's way above would be best. If you need to do it through PHP, this method should work. Save your excel file as csv.
$rows = file('textfile.csv');
for($i = 0; $i < sizeof($rows); $i++) {
list($field1, $field2, $field3) = explode(',', $rows[$i]);
$query = "insert into tableName values ('$field1', '$field2', '$field3')";
mysql_query($query);
}