PHP mysqli_num_fields() 函数

定义和用法

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

mysqli_num_fields() 函数接受结果对象作为参数，检索并返回给定对象中的字段数。

语法

mysqli_num_fields($result);

参数

返回值

PHP mysqli_num_fields() 函数返回一个整数值，指定给定结果对象中的字段数。

PHP 版本

此函数首次在 PHP 5 版本中引入，并在所有后续版本中均有效。

示例

以下示例演示了 mysqli_num_fields() 函数（过程式风格）的用法：

<?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
   $result = mysqli_query($con, "SELECT * FROM myplayers");

   //Number of fields
   $count = mysqli_num_fields($result);
   print("Number of fields in the result: ".$count);

   //Closing the statement
   mysqli_free_result($result);

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

这将产生以下结果：

Table Created.....
Record Inserted.....
Number of fields in the result: 5

示例

在面向对象风格中，此函数的语法为 $result->field_count; 以下是此函数在面向对象风格中的示例：

<?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();

   //Number of fields
   $count = $result->field_count;
   print("Number of fields in the result: ".$count);

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

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

这将产生以下结果：

Table Created.....
Number of fields in the result: 2