mysqli_stmt::result_metadata

mysqli_stmt_result_metadata

(PHP 5, PHP 7, PHP 8)

mysqli_stmt::result_metadata -- mysqli_stmt_result_metadata — Returns result set metadata from a prepared statement

说明

面向对象风格

public mysqli_stmt::result_metadata ( ) : mysqli_result|false

过程化风格

mysqli_stmt_result_metadata ( mysqli_stmt $statement ) : mysqli_result|false

If a statement passed to mysqli_prepare() is one that produces a result set, mysqli_stmt_result_metadata() returns the result object that can be used to process the meta information such as total number of fields and individual field information.

Note:
This result set pointer can be passed as an argument to any of the field-based functions that process result set metadata, such as:

mysqli_num_fields()

mysqli_fetch_field()

mysqli_fetch_field_direct()

mysqli_fetch_fields()

mysqli_field_count()

mysqli_field_seek()

mysqli_field_tell()

mysqli_free_result()

The result set structure should be freed when you are done with it, which you can do by passing it to mysqli_free_result()

Note:
The result set returned by mysqli_stmt_result_metadata() contains only metadata. It does not contain any row results. The rows are obtained by using the statement handle with mysqli_stmt_fetch().

参数

stmt: 仅以过程化样式：由 mysqli_stmt_init() 返回的 statement 标识。

返回值

Returns a result object or false if an error occurred.

范例

Example #1 面向对象风格


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

$mysqli->query("DROP TABLE IF EXISTS friends");
$mysqli->query("CREATE TABLE friends (id int, name varchar(20))");

$mysqli->query("INSERT INTO friends VALUES (1,'Hartmut'), (2, 'Ulf')");

$stmt = $mysqli->prepare("SELECT id, name FROM friends");
$stmt->execute();

/* get resultset for metadata */
$result = $stmt->result_metadata();

/* retrieve field information from metadata result set */
$field = $result->fetch_field();

printf("Fieldname: %s\n", $field->name);

/* close resultset */
$result->close();

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

Example #2 过程化风格


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

mysqli_query($link, "DROP TABLE IF EXISTS friends");
mysqli_query($link, "CREATE TABLE friends (id int, name varchar(20))");

mysqli_query($link, "INSERT INTO friends VALUES (1,'Hartmut'), (2, 'Ulf')");

$stmt = mysqli_prepare($link, "SELECT id, name FROM friends");
mysqli_stmt_execute($stmt);

/* get resultset for metadata */
$result = mysqli_stmt_result_metadata($stmt);

/* retrieve field information from metadata result set */
$field = mysqli_fetch_field($result);

printf("Fieldname: %s\n", $field->name);

/* close resultset */
mysqli_free_result($result);

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

参见

mysqli_prepare() - 准备执行一个 SQL 语句
mysqli_free_result() - Frees the memory associated with a result

User Contributed Notes

potherca at gmail dot com 15-Apr-2010 12:52


If result_metadata() returns false but error/errno/sqlstate tells you no error occurred, this means your query is one that does not produce a result set, i.e. an INSERT/UPDATE/DELETE query instead of a SELECT query.



This is stated in the documentation where it says "If a statement passed to mysqli_prepare() is one that produces a result set, mysqli_stmt_result_metadata() returns the result object", but it might not be clear to everyone what this entails exactly. 



Hope this helps.