PDOStatement::getColumnMeta

(PHP 5 >= 5.1.0, PHP 7, PECL pdo >= 0.2.0)

PDOStatement::getColumnMeta — Returns metadata for a column in a result set

Description

public array PDOStatement::getColumnMeta ( int $column )

Warning

This function is EXPERIMENTAL. The behaviour of this function, its name, and surrounding documentation may change without notice in a future release of PHP. This function should be used at your own risk.

Retrieves the metadata for a 0-indexed column in a result set as an associative array.

Warning

Not all PDO drivers support PDOStatement::getColumnMeta().

Parameters

column: The 0-indexed column in the result set.

Return Values

Returns an associative array containing the following values representing the metadata for a single column:

**Column metadata**
Name	Value
native_type	The PHP native type used to represent the column value.
driver:decl_type	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	Any flags set for this column.
name	The name of this column as returned by the database.
table	The name of this column's table as returned by the database.
len	The length of this column. Normally -1 for types other than floating point decimals.
precision	The numeric precision of this column. Normally 0 for types other than floating point decimals.
pdo_type	The type of this column as represented by the PDO::PARAM_* constants.

Returns FALSE if the requested column does not exist in the result set, or if no result set exists.

Changelog

Version	Description
5.2.3	table field

Examples

Example #1 Retrieving column metadata

The following example shows the results of retrieving the metadata for a single column generated by a function (COUNT) in a PDO_SQLITE driver.


<?php
$select = $DB->query('SELECT COUNT(*) FROM fruit');
$meta = $select->getColumnMeta(0);
var_dump($meta);
?>

The above example will output:

array(6) {
  ["native_type"]=>
  string(7) "integer"
  ["flags"]=>
  array(0) {
  }
  ["name"]=>
  string(8) "COUNT(*)"
  ["len"]=>
  int(-1)
  ["precision"]=>
  int(0)
  ["pdo_type"]=>
  int(2)
}

User Contributed Notes

colin at fusionbox dot com

7 years ago


This method is supported in the MySQL 5.0+ driver.  It can be used for object hydration:

<?php

$pdo_stmt = $dbh->execute('SELECT discussion.id, discussion.text, comment.id, comment.text FROM discussions LEFT JOIN comments ON comment.discussion_id = discussion.id');

foreach(range(0, $pdo_stmt->columnCount() - 1) as $column_index)
{
  $meta[] = $pdo_stmt->getColumnMeta($column_index);
}

while($row = $pdo_stmt->fetch(PDO::FETCH_NUM))
{
  foreach($row as $column_index => $column_value)
  {
    //do something with the data, using the ids to establish the discussion.has_many(comments) relationship.
  }
}

?>

If you are building an ORM, this method is very useful to support more natural SQL syntax.  Most ORMs require the column names to be aliases so that they can be parsed and turned into objects that properly represent has_one, has_many, many_to_many relationships.

asohn aircanopy net

8 years ago


I found a short discussion related to this function at 
http://www.sitepoint.com/forums/showthread.php?t=497257

I haven't tried it (yet?) but hopefully someone can find it useful.