PDOStatement::getColumnMeta

Article
11/18/2022

Retrieves metadata for a column.

Syntax

  
array PDOStatement::getColumnMeta ( $column );

Parameters

$conn: (Integer) The zero-based number of the column whose metadata you want to retrieve.

Return Value

An associative array (key and value) containing the metadata for the column. See the Remarks section for a description of the fields in the array.

Remarks

The following table describes the fields in the array returned by getColumnMeta.

NAME	VALUES
native_type	Specifies the PHP type for column. Always string.
driver:decl_type	Specifies the SQL type used to represent the column value in the database. If the column in the result set is the result of a function, this value is not returned by PDOStatement::getColumnMeta.
flags	Specifies the flags set for this column. Always 0.
name	Specifies the name of the column in the database.
table	Specifies the name of the table that contains the column in the database. Always blank.
len	Specifies the column length.
precision	Specifies the numeric precision of this column.
pdo_type	Specifies the type of this column as represented by the PDO::PARAM_* constants. Always PDO::PARAM_STR (2).

Support for PDO was added in version 2.0 of the Microsoft Drivers for PHP for SQL Server.

Example

<?php  
$database = "AdventureWorks";  
$server = "(local)";  
$conn = new PDO( "sqlsrv:server=$server ; Database = $database", "", "");  
  
$stmt = $conn->query("select * from Person.ContactType");  
$metadata = $stmt->getColumnMeta(2);  
var_dump($metadata);  
  
print $metadata['sqlsrv:decl_type'] . "\n";  
print $metadata['native_type'] . "\n";  
print $metadata['name'];  
?>

Sensitivity Data Classification Metadata

Beginning with version 5.8.0, a new statement attribute PDO::SQLSRV_ATTR_DATA_CLASSIFICATION is available for users to access the sensitivity data classification metadata in Microsoft SQL Server 2019 using PDOStatement::getColumnMeta, which requires Microsoft ODBC Driver 17.4.2 or above.

Note the attribute PDO::SQLSRV_ATTR_DATA_CLASSIFICATION is false by default, but when set to true, the aforementioned array field, flags, will be populated with the sensitivity data classification metadata, if it exists.

Take a Patients table for example:

CREATE TABLE Patients 
      [PatientId] int identity,
      [SSN] char(11),
      [FirstName] nvarchar(50),
      [LastName] nvarchar(50),
      [BirthDate] date)

We can classify the SSN and BirthDate columns as shown below:

ADD SENSITIVITY CLASSIFICATION TO [Patients].SSN WITH (LABEL = 'Highly Confidential - secure privacy', INFORMATION_TYPE = 'Credentials')
ADD SENSITIVITY CLASSIFICATION TO [Patients].BirthDate WITH (LABEL = 'Confidential Personal Data', INFORMATION_TYPE = 'Birthdays')

To access the metadata, use PDOStatement::getColumnMeta after setting PDO::SQLSRV_ATTR_DATA_CLASSIFICATION to true, as shown in the snippet below:

$options = array(PDO::SQLSRV_ATTR_DATA_CLASSIFICATION => true);
$tableName = 'Patients';
$tsql = "SELECT * FROM $tableName";
$stmt = $conn->prepare($tsql, $options);
$stmt->execute();
$numCol = $stmt->columnCount();

for ($i = 0; $i < $numCol; $i++) {
    $metadata = $stmt->getColumnMeta($i);
    $jstr = json_encode($metadata);
    echo $jstr . PHP_EOL;
}

The output of metadata for all columns is:

{"flags":{"Data Classification":[]},"sqlsrv:decl_type":"int identity","native_type":"string","table":"","pdo_type":2,"name":"PatientId","len":10,"precision":0}
{"flags":{"Data Classification":[{"Label":{"name":"Highly Confidential - secure privacy","id":""},"Information Type":{"name":"Credentials","id":""}}]},"sqlsrv:decl_type":"char","native_type":"string","table":"","pdo_type":2,"name":"SSN","len":11,"precision":0}
{"flags":{"Data Classification":[]},"sqlsrv:decl_type":"nvarchar","native_type":"string","table":"","pdo_type":2,"name":"FirstName","len":50,"precision":0}
{"flags":{"Data Classification":[]},"sqlsrv:decl_type":"nvarchar","native_type":"string","table":"","pdo_type":2,"name":"LastName","len":50,"precision":0}
{"flags":{"Data Classification":[{"Label":{"name":"Confidential Personal Data","id":""},"Information Type":{"name":"Birthdays","id":""}}]},"sqlsrv:decl_type":"date","native_type":"string","table":"","pdo_type":2,"name":"BirthDate","len":10,"precision":0}

If we modify the above snippet by setting PDO::SQLSRV_ATTR_DATA_CLASSIFICATION to false (the default case), the flags field will always be 0 as before, like this:

{"flags":0,"sqlsrv:decl_type":"int identity","native_type":"string","table":"","pdo_type":2,"name":"PatientId","len":10,"precision":0}
{"flags":0,"sqlsrv:decl_type":"char","native_type":"string","table":"","pdo_type":2,"name":"SSN","len":11,"precision":0}
{"flags":0,"sqlsrv:decl_type":"nvarchar","native_type":"string","table":"","pdo_type":2,"name":"FirstName","len":50,"precision":0}
{"flags":0,"sqlsrv:decl_type":"nvarchar","native_type":"string","table":"","pdo_type":2,"name":"LastName","len":50,"precision":0}
{"flags":0,"sqlsrv:decl_type":"date","native_type":"string","table":"","pdo_type":2,"name":"BirthDate","len":10,"precision":0}

Sensitivity Rank using a predefined set of values

Beginning with 5.9.0, PHP drivers added classification rank retrieval when using ODBC Driver 17.4.2 or above. The user may define rank when using ADD SENSITIVITY CLASSIFICATION to classify any data column.

For example, if the user assigns NONE and LOW to BirthDate and SSN respectively, the JSON representation is shown as follows:

{"0":{"Label":{"name":"Confidential Personal Data","id":""},"Information Type":{"name":"Birthdays","id":""},"rank":0},"rank":0}
{"0":{"Label":{"name":"Highly Confidential - secure privacy","id":""},"Information Type":{"name":"Credentials","id":""},"rank":10},"rank":10}

As shown in sensitivity classification, the numerical values of the ranks are:

0 for NONE
10 for LOW
20 for MEDIUM
30 for HIGH
40 for CRITICAL

Hence, if instead of RANK=NONE, the user defines RANK=CRITICAL when classifying the column BirthDate, the classification metadata will be:

array(1) {
  ["Data Classification"]=>
  array(2) {
    [0]=>
    array(3) {
      ["Label"]=>
      array(2) {
        ["name"]=>
        string(26) "Confidential Personal Data"
        ["id"]=>
        string(0) ""
      }
      ["Information Type"]=>
      array(2) {
        ["name"]=>
        string(9) "Birthdays"
        ["id"]=>
        string(0) ""
      }
      ["rank"]=>
      int(40)
    }
    ["rank"]=>
    int(40)
  }
}

The updated JSON representation is shown below:

{"0":{"Label":{"name":"Confidential Personal Data","id":""},"Information Type":{"name":"Birthdays","id":""},"rank":40},"rank":40}