PHP mysqli_free_result()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_free_result() 函数接受一个结果对象作为参数并释放与之关联的内存。

用法

mysqli_free_result($result);

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。

返回值

此函数不返回任何值。

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_free_result() 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");

   print("Contents of the resultset...\n");
   //Contents of the resultset
   while ($row = mysqli_fetch_row($res)) {
      print("ID:".$row[0]."\n");
      print("First_Name:".$row[1]."\n");
      print("Last_Name:".$row[2]."\n");
      print("Place_Of_Birth:".$row[3]."\n");
      print("Country:".$row[4]."\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.....
Contents of the resultset...
ID:1
First_Name:Sikhar
Last_Name:Dhawan
Place_Of_Birth:Delhi
Country:India
ID:2
First_Name:Jonathan
Last_Name:Trott
Place_Of_Birth:CapeTown
Country:SouthAfrica
ID:3
First_Name:Kumara
Last_Name:Sangakkara
Place_Of_Birth:Matale
Country:Srilanka

如果您尝试在将其释放后获取结果的内容 -

$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");

//Closing the statement
mysqli_free_result($res);

print("Contents of the resultset...\n");
//Contents of the resultset
while ($row = mysqli_fetch_row($res)) {
   print("ID:".$row[0]."\n");
   print("First_Name:".$row[1]."\n");
   print("Last_Name:".$row[2]."\n");
   print("Place_Of_Birth:".$row[3]."\n");
   print("Country:".$row[4]."\n");
}

//Closing the connection
mysqli_close($con);

您将收到如下所示的错误 -

Table Created.....
Record Inserted.....
Contents of the resultset...
PHP Warning: mysqli_fetch_row():Couldn't fetch mysqli_result in E:\PHPExamples\procedure_oriented.php on line 19

Warning:mysqli_fetch_row():Couldn't fetch mysqli_result in E:\PHPExamples\procedure_oriented.php on line 19

示例

在面向对象的风格中，这个函数的语法是 $result->close();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();

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

   //Closing the result
   $result->close();

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

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

这将产生以下结果 -

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