Metadata

A MySQL result set contains metadata. The metadata describes the columns found in the result set. All metadata send by MySQL is accessible through the mysqli interface. The extension performs no or negliable changes to the information it receives. Differences between MySQL server versions are not aligned.

Meta data is access through the mysqli_result interface.

Пример #1 Accessing result set meta data


<?php
$mysqli = new mysqli("example.com", "user", "password", "database");
if ($mysqli->connect_errno)
 echo "Failed to connect to MySQL: (" . $mysqli->connect_errno . ") " . $mysqli->connect_error;

$res = $mysqli->query("SELECT 1 AS _one, 'Hello' AS _two FROM DUAL");
var_dump($res->fetch_fields());
?>

Результат выполнения данного примера:

array(2) {
  [0]=>
  object(stdClass)#3 (13) {
    ["name"]=>
    string(4) "_one"
    ["orgname"]=>
    string(0) ""
    ["table"]=>
    string(0) ""
    ["orgtable"]=>
    string(0) ""
    ["def"]=>
    string(0) ""
    ["db"]=>
    string(0) ""
    ["catalog"]=>
    string(3) "def"
    ["max_length"]=>
    int(1)
    ["length"]=>
    int(1)
    ["charsetnr"]=>
    int(63)
    ["flags"]=>
    int(32897)
    ["type"]=>
    int(8)
    ["decimals"]=>
    int(0)
  }
  [1]=>
  object(stdClass)#4 (13) {
    ["name"]=>
    string(4) "_two"
    ["orgname"]=>
    string(0) ""
    ["table"]=>
    string(0) ""
    ["orgtable"]=>
    string(0) ""
    ["def"]=>
    string(0) ""
    ["db"]=>
    string(0) ""
    ["catalog"]=>
    string(3) "def"
    ["max_length"]=>
    int(5)
    ["length"]=>
    int(5)
    ["charsetnr"]=>
    int(8)
    ["flags"]=>
    int(1)
    ["type"]=>
    int(253)
    ["decimals"]=>
    int(31)
  }
}

Prepared statements

Meta data of result sets created using prepared statements are accessed the same way. A suitable mysqli_result handle is returned by mysqli_stmt_result_metadata().

Пример #2 Prepared statements metadata


<?php
$stmt = $mysqli->prepare("SELECT 1 AS _one, 'Hello' AS _two FROM DUAL");
$stmt->execute();
$res = $stmt->result_metadata();
var_dump($res->fetch_fields());
?>

See also