betterCode() PHP 2025

    mysqli_result::fetch_field

    mysqli_fetch_field

    (PHP 5, PHP 7, PHP 8)

    mysqli_result::fetch_field -- mysqli_fetch_field — Returns the next field in the result set

    说明

    面向对象风格

    public mysqli_result::fetch_field(): object|false

    过程化风格

    mysqli_fetch_field(mysqli_result $result): object|false

    Returns the definition of one column of a result set as an object. Call this function repeatedly to retrieve information about all columns in the 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。

    返回值

    Returns an object which contains field definition information or false if no field information 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 Code LIMIT 5";

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

    /* Get field information for all columns */
    while ($finfo = $result->fetch_field()) {

    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\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 Code LIMIT 5";

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

    /* Get field information for all fields */
    while ($finfo = mysqli_fetch_field($result)) {

    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\n", $finfo->type);
    }
    mysqli_free_result($result);
    }

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

    以上示例会输出：

    Name:     Name
Table:    Country
max. Len: 11
Flags:    1
Type:     254

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

    参见

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    用户贡献的备注 8 notes

    up
    52
    iansoko at hotmail dot com
    14 years ago
    here are the data types that correspond to the TYPE number returned by fetch_field.

    thought i would post this here since i couldn't find the info elsewhere.

    numerics
    -------------
    BIT: 16
    TINYINT: 1
    BOOL: 1
    SMALLINT: 2
    MEDIUMINT: 9
    INTEGER: 3
    BIGINT: 8
    SERIAL: 8
    FLOAT: 4
    DOUBLE: 5
    DECIMAL: 246
    NUMERIC: 246
    FIXED: 246

    dates
    ------------
    DATE: 10
    DATETIME: 12
    TIMESTAMP: 7
    TIME: 11
    YEAR: 13

    strings & binary
    ------------
    CHAR: 254
    VARCHAR: 253
    ENUM: 254
    SET: 254
    BINARY: 254
    VARBINARY: 253
    TINYBLOB: 252
    BLOB: 252
    MEDIUMBLOB: 252
    TINYTEXT: 252
    TEXT: 252
    MEDIUMTEXT: 252
    LONGTEXT: 252
    up
    15
    ragtag at hotmail dot com
    17 years ago
    The flags used by MySql are:
    NOT_NULL_FLAG = 1
    PRI_KEY_FLAG = 2
    UNIQUE_KEY_FLAG = 4
    BLOB_FLAG = 16
    UNSIGNED_FLAG = 32
    ZEROFILL_FLAG = 64
    BINARY_FLAG = 128
    ENUM_FLAG = 256
    AUTO_INCREMENT_FLAG = 512
    TIMESTAMP_FLAG = 1024
    SET_FLAG = 2048
    NUM_FLAG = 32768
    PART_KEY_FLAG = 16384
    GROUP_FLAG = 32768
    UNIQUE_FLAG = 65536

    To test if a flag is set you can use & like so:
    <?php
    $meta     = $mysqli_result_object->fetch_field();
    if (    $meta->flags & 4) {
    echo     'Unique key flag is set';
    }
    ?>
    up
    3
    andre at koethur dot de
    11 years ago
    Here are two methods for converting the 'type' and 'flags' attributes to text for debugging purposes. They both use the predefined MYSQLI_ constants to generate the text.

    <?php

    public static function h_type2txt($type_id)
    {
    static     $types;

    if (!isset(    $types))
    {
    $types = array();
    $constants = get_defined_constants(true);
    foreach (    $constants['mysqli'] as $c => $n) if (preg_match('/^MYSQLI_TYPE_(.*)/', $c, $m)) $types[$n] = $m[1];
    }

    return     array_key_exists($type_id, $types)? $types[$type_id] : NULL;
    }

    public static function     h_flags2txt($flags_num)
    {
    static     $flags;

    if (!isset(    $flags))
    {
    $flags = array();
    $constants = get_defined_constants(true);
    foreach (    $constants['mysqli'] as $c => $n) if (preg_match('/MYSQLI_(.*)_FLAG$/', $c, $m)) if (!array_key_exists($n, $flags)) $flags[$n] = $m[1];
    }

    $result = array();
    foreach (    $flags as $n => $t) if ($flags_num & $n) $result[] = $t;
    return     implode(' ', $result);
    }

    ?>
    up
    1
    sofe2038 at gmail dot com
    7 years ago
    The constants in a few other comments above appear to be inaccurate. Here are some more official references that seem quite hard to search.

    The "type" attribute: https://dev.mysql.com/doc/internals/en/com-query-response.html#column-type
    The "flags" attribute: https://github.com/google/mysql/blob/master/include/mysql_com.h#L133

    In addition, all attributes are explained on the COM_QUERY_RESPONSE page too: https://dev.mysql.com/doc/internals/en/com-query-response.html#column-definition
    up
    1
    rvila at revolutionvisualarts dot com
    9 years ago
    The predefined constant values returned by the function get_predefined_constants() for:

    MYSQLI_TYPE_CHAR = 1
    MYSQLI _TYPE_TINYINT = 1

    If the code is used to categorized the type of field use this values will of course create confusion. For example:

    if($fieldtype === "CHAR"){
    $field_html_attribute = "text";
    $field_html_length = 1;
    } elseif($fieldtype === "TINYINT") {
    $field_html_attribute = "number";
    $field_html_length = 1;
    }

    If an array is created to set the key as the numeric value and the value of that key as the the text title, TINYINT will be replaced by CHAR value. But is this process is reversed, then the code will select TINYINT if the foreach statement set to break when the numeric value of the flag equals the value of the current key as the first intance.

    Base in the note added by Johnathan at http://php.net/manual/en/mysqli.field-count.php the values should be:

    CHAR = 254
    TINYINT = 1

    But predefined function attributes the value 254 to MYSQLI_TYPE_STRING.

    Just for FYI
    up
    2
    miqrogroove at gmail dot com
    12 years ago
    Beware the values of the predefined constants. They do not always correlate with the actual field types. For example:

    MYSQLI_TYPE_BLOB: 252
    MYSQLI_TYPE_TINY_BLOB: 249
    MYSQLI_TYPE_MEDIUM_BLOB: 250
    MYSQLI_TYPE_LONG_BLOB: 251

    MySQLi will indeed return a value of 252 for a tinytext field, but as you can see, this does not correspond to the value of MYSQLI_TYPE_TINY_BLOB.
    up
    0
    nick
    7 years ago
    It is not possible to get the values for an enum or set field through fetch_fields(). As far as I can tell this is because it hasn't been implemented in the mysqlnd api but whatever the reason it is not possible and you must issue a query like SHOW COLUMNS directly and interrogate the result to determine them.

    Incidentally you need to check the enum_flag rather than look for the enum_type to determine whether a field is enum or not. The type returned is usually some kind of string.
    up
    2
    Anonymous
    13 years ago
    The constants for the TYPE number returned by fetch_field are enumerated here (MYSQLI_TYPE_*):
    http://php.net/manual/en/mysqli.constants.php
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