mysqli_stmt::result_metadata()
(PHP 5, PHP 7)
Returns result set metadata from a prepared statement
说明
面向对象风格
mysqli_stmt::result_metadata(void): mysqli_result
过程化风格
mysqli_stmt_result_metadata(mysqli_stmt$stmt): mysqli_result
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
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.