Just a note regarding the size of Oracle  NUMBERS will always return 22 as their "size".
This seems to be an Oracle feature. The rest of the documentation is in bug5156.(PHP 5, PHP 7, PHP 8, PECL OCI8 >= 1.1.0)
oci_field_size — Returns field's size
   Returns the size of a column. 
  
statementA valid OCI statement identifier.
columnCan be the field's index (1-based) or name.
   Returns the size of a column in bytes, başarısızlık durumunda false döner
  
Örnek 1 oci_field_size() example
<?php
// Create the table with:
//   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); // Use OCI_DESCRIBE_ONLY if not fetching rows
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";
// Outputs:
//    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);
?>
Just a note regarding the size of Oracle  NUMBERS will always return 22 as their "size".
This seems to be an Oracle feature. The rest of the documentation is in bug5156.