PHP mysqli_fetch_field_direct()用法及代码示例

定义和用法

PHP 结果对象(属于 mysqli_result 类)表示 MySQL 结果，由 SELECT 或 DESCRIBE 或 EXPLAIN 查询返回。

mysqli_fetch_field_direct()函数接受一个结果对象和一个表示字段编号的整数作为参数，并以对象的形式返回指定列/字段的定义信息。

用法

mysqli_fetch_field_direct($result, $field);

参数

Sr.No	参数及说明
1	result(Mandatory) 这是一个表示结果对象的标识符。
2	field(Mandatory) 一个整数值，表示您需要元数据/definition-information 的字段。

返回值

PHP mysqli_fetch_field_direct() 函数返回一个包含指定字段定义信息的对象。如果指定的字段(数字)不可用，此函数将返回 FALSE。

返回的对象包含以下属性 $minus;

• name

• orgname

• table

• orgtable

• max_length

• length

• charsetnr

• flags

• type

• decimals

PHP版本

这个函数最初是在 PHP 版本 5 中引入的，适用于所有后续版本。

示例

以下示例演示了 mysqli_fetch_field_direct() 函数的用法(程序风格) -

<?php
   $con = mysqli_connect("localhost", "root", "password", "mydb");

   mysqli_query($con, "CREATE TABLE myplayers(ID INT, First_Name VARCHAR(255), Last_Name VARCHAR(255), Place_Of_Birth VARCHAR(255), Country VARCHAR(255))");
   print("Table Created.....\n");
   mysqli_query($con, "INSERT INTO myplayers values(1, 'Sikhar', 'Dhawan', 'Delhi', 'India')");
   mysqli_query($con, "INSERT INTO myplayers values(2, 'Jonathan', 'Trott', 'CapeTown', 'SouthAfrica')");
   mysqli_query($con, "INSERT INTO myplayers values(3, 'Kumara', 'Sangakkara', 'Matale', 'Srilanka')");
   print("Record Inserted.....\n");

   //Retrieving the contents of the table
   $res = mysqli_query($con, "SELECT * FROM myplayers");

   //Fetching the metadata of 3rd field
   $info = mysqli_fetch_field_direct($res, 2);

   print("Name:".$info->name."\n");
   print("Table:".$info->table."\n");
   print("Max Length:".$info->max_length."\n");
   print("Flags:".$info->flags."\n");
   print("Type:".$info->type."\n");
   print("Definition:".$info->def."\n");
   print("Character Set:".$info->charsetnr."\n");

   //Closing the statement
   mysqli_free_result($res);

   //Closing the connection
   mysqli_close($con);
?>

这将产生以下结果 -

Table Created.....
Record Inserted.....
Name:Last_Name
Table:myplayers
Max Length:10
Flags:0
Type:253

示例

在面向对象的风格中，这个函数的语法是 $result->fetch_field_direct();以下是面向对象样式 $minus 中此函数的示例；

<?php
   //Creating a connection
   $con = new mysqli("localhost", "root", "password", "mydb");

   $con -> query("CREATE TABLE Test(Name VARCHAR(255), AGE INT)");
   $con -> query("insert into Test values('Raju', 25),('Rahman', 30),('Sarmista', 27)");
   print("Table Created.....\n");

   $stmt = $con -> prepare( "SELECT * FROM Test WHERE Name in(?, ?)");
   $stmt -> bind_param("ss", $name1, $name2);
   $name1 = 'Raju';
   $name2 = 'Rahman';

   //Executing the statement
   $stmt->execute();

   //Retrieving the result
   $result = $stmt->get_result();

   //Fetching the metadata of 2nd field
   $info = $result->fetch_field_direct(1);

   print("Name:".$info->name."\n");
   print("Table:".$info->table."\n");
   print("Max Length:".$info->max_length."\n");
   print("Flags:".$info->flags."\n");
   print("Type:".$info->type."\n");
   print("Definition:".$info->def."\n");
   print("Character Set:".$info->charsetnr."\n");

   //Closing the statement
   $stmt->close();

   //Closing the connection
   $con->close();
?>

这将产生以下结果 -

Table Created.....
Name:AGE
Table:Test
Max Length:0
Flags:32768
Type:3
Definition:
Character Set:63