# 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.

This function returns an empty mysqli_result object which can be used to access metadata information from the prepared statement without having to fetch the actual rows of data. There is no need to use this function when using mysqli_stmt_get_result() to retrieve the entire result set from a prepared statement as a result object.

> 注意:

> This result set object can be passed as an argument only to 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()

> 注意: The result set returned by mysqli_stmt_result_metadata() contains only metadata. It does not contain any row results. The rows are obtained by calling mysqli_stmt_get_result() on the statement handle or with mysqli_stmt_fetch().

### 参数

`statement`

  仅以过程化样式：由 mysqli_stmt_init() 返回的 mysqli_stmt 对象。

### 返回值

Returns a result object or `false` if an error occurred. If the statement does not produce a result set, `false` is returned as well.

### 错误／异常

If mysqli error reporting is enabled (`MYSQLI_REPORT_ERROR`) and the requested operation fails, a warning is generated. If, in addition, the mode is set to `MYSQLI_REPORT_STRICT`, a mysqli_sql_exception is thrown instead.

### 示例

示例 #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);
?>`

示例 #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);
?>`

### 参见

- mysqli_prepare() - 预处理执行 SQL
- mysqli_free_result() - Frees the memory associated with a result
- mysqli_stmt_get_result() - Gets a result set from a prepared statement as a mysqli_result object

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