MySQL 结果集包含元数据。元数据描述结果集中找到的列。通过 mysqli 接口可以访问 MySQL 发送的所有元数据。扩展对它接收的信息进行的更改很少或没有更改。MySQL 服务器版本之间的差异不会对齐。
元数据通过 mysqli_result 接口访问。
示例 #1 访问结果集元数据
<?php
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$mysqli = new mysqli("example.com", "user", "password", "database");
$result = $mysqli->query("SELECT 1 AS _one, 'Hello' AS _two FROM DUAL");
var_dump($result->fetch_fields());上面的例子将输出
array(2) {
[0]=>
object(stdClass)#3 (13) {
["name"]=>
string(4) "_one"
["orgname"]=>
string(0) ""
["table"]=>
string(0) ""
["orgtable"]=>
string(0) ""
["def"]=>
string(0) ""
["db"]=>
string(0) ""
["catalog"]=>
string(3) "def"
["max_length"]=>
int(1)
["length"]=>
int(1)
["charsetnr"]=>
int(63)
["flags"]=>
int(32897)
["type"]=>
int(8)
["decimals"]=>
int(0)
}
[1]=>
object(stdClass)#4 (13) {
["name"]=>
string(4) "_two"
["orgname"]=>
string(0) ""
["table"]=>
string(0) ""
["orgtable"]=>
string(0) ""
["def"]=>
string(0) ""
["db"]=>
string(0) ""
["catalog"]=>
string(3) "def"
["max_length"]=>
int(5)
["length"]=>
int(5)
["charsetnr"]=>
int(8)
["flags"]=>
int(1)
["type"]=>
int(253)
["decimals"]=>
int(31)
}
}
预处理语句
使用预处理语句创建的结果集的元数据以相同的方式访问。合适的 mysqli_result 句柄由 mysqli_stmt::result_metadata() 返回。
示例 #2 预处理语句元数据
<?php
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$mysqli = new mysqli("example.com", "user", "password", "database");
$stmt = $mysqli->prepare("SELECT 1 AS _one, 'Hello' AS _two FROM DUAL");
$stmt->execute();
$result = $stmt->result_metadata();
var_dump($result->fetch_fields());参见