oci_field_size

<?php

// Создайте таблицу:
//   CREATE TABLE mytab (number_col NUMBER, varchar2_col varchar2(1),
//                       clob_col CLOB, date_col DATE);

$conn = oci_connect("hr", "hrpwd", "localhost/XE");
if (!$conn) {
    $m = oci_error();
    trigger_error(htmlentities($m['message']), E_USER_ERROR);
}

$stid = oci_parse($conn, "SELECT * FROM mytab");
oci_execute($stid, OCI_DESCRIBE_ONLY); // // используйте OCI_DESCRIBE_ONLY, если не получаете данных

echo "<table border=\"1\">\n";
echo "<tr>";
echo "<th>Name</th>";
echo "<th>Type</th>";
echo "<th>Length</th>";
echo "</tr>\n";

$ncols = oci_num_fields($stid);

for ($i = 1; $i <= $ncols; $i++) {
    $column_name  = oci_field_name($stid, $i);
    $column_type  = oci_field_type($stid, $i);
    $column_size  = oci_field_size($stid, $i);

    echo "<tr>";
    echo "<td>$column_name</td>";
    echo "<td>$column_type</td>";
    echo "<td>$column_size</td>";
    echo "</tr>\n";
}

echo "</table>\n";

// Выведет:
//    Name           Type       Length
//    NUMBER_COL    NUMBER        22
//    VARCHAR2_COL  VARCHAR2       1
//    CLOB_COL      CLOB        4000
//    DATE_COL      DATE           7

oci_free_statement($stid);
oci_close($conn);

?>