Fetch meta-data for a single field

# mysqli_result::fetch_field_direct

# mysqli_fetch_field_direct

(PHP 5, PHP 7, PHP 8)

mysqli_result::fetch_field_direct -- mysqli_fetch_field_direct — Fetch meta-data for a single field

### 说明

面向对象风格

public function mysqli_result::fetch_field_direct(int `$index`): object|false

过程化风格

function mysqli_fetch_field_direct(mysqli_result `$result`, int `$index`): object|false

Returns an object which contains field definition information from the specified result set.

### 参数

`result`
  仅以过程化样式：由 mysqli_query()、mysqli_store_result()、 mysqli_use_result()、mysqli_stmt_get_result() 返回的 mysqli_result 对象。
`index`

  The field number. This value must be in the range from `0` to `number of fields - 1`.

### 返回值

Returns an object which contains field definition information or `false` if no field information for specified `index` is available.

Object properties
Property | Description
--- | ---
name | The name of the column
orgname | Original column name if an alias was specified
table | The name of the table this field belongs to (if not calculated)
orgtable | Original table name if an alias was specified
def | Unused. Always an empty string
db | The name of the database
catalog | Unused. Always `"def"`
max_length | The maximum width of the field for the result set. As of PHP 8.1, this value is always `0`.
length | The width of the field in bytes. For string columns, the length value varies on the connection character set. For example, if the character set is `latin1`, a single-byte character set, the length value for a `SELECT 'abc'` query is 3. If the character set is `utf8mb4`, a multibyte character set in which characters take up to 4 bytes, the length value is 12.
charsetnr | The character set number for the field.
flags | An integer representing the bit-flags for the field.
type | The data type used for this field
decimals | The number of decimals for numeric fields, and the fractional seconds precision for temporal fields.

### 示例

示例 #1 面向对象风格

    <?php
    $mysqli = new mysqli("localhost", "my_user", "my_password", "world");

    /* check connection */
    if (mysqli_connect_errno()) {
        printf("Connect failed: %s\n", mysqli_connect_error());
        exit();
    }

    $query = "SELECT Name, SurfaceArea from Country ORDER BY Name LIMIT 5";

    if ($result = $mysqli->query($query)) {

        /* Get field information for column 'SurfaceArea' */
        $finfo = $result->fetch_field_direct(1);

        printf("Name:     %s\n", $finfo->name);
        printf("Table:    %s\n", $finfo->table);
        printf("max. Len: %d\n", $finfo->max_length);
        printf("Flags:    %d\n", $finfo->flags);
        printf("Type:     %d\n", $finfo->type);

        $result->close();
    }

    /* close connection */
    $mysqli->close();
    ?>

示例 #2 过程化风格

    <?php
    $link = mysqli_connect("localhost", "my_user", "my_password", "world");

    /* check connection */
    if (mysqli_connect_errno()) {
        printf("Connect failed: %s\n", mysqli_connect_error());
        exit();
    }

    $query = "SELECT Name, SurfaceArea from Country ORDER BY Name LIMIT 5";

    if ($result = mysqli_query($link, $query)) {

        /* Get field information for column 'SurfaceArea' */
        $finfo = mysqli_fetch_field_direct($result, 1);

        printf("Name:     %s\n", $finfo->name);
        printf("Table:    %s\n", $finfo->table);
        printf("max. Len: %d\n", $finfo->max_length);
        printf("Flags:    %d\n", $finfo->flags);
        printf("Type:     %d\n", $finfo->type);

        mysqli_free_result($result);
    }

    /* close connection */
    mysqli_close($link);
    ?>

以上示例会输出：

    Name:     SurfaceArea
    Table:    Country
    max. Len: 10
    Flags:    32769
    Type:     4

### 参见

- mysqli_num_fields() - Gets the number of fields in the result set
- mysqli_fetch_field() - Returns the next field in the result set
- mysqli_fetch_fields() - Returns an array of objects representing the fields in a result set

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