PHP mysqli_fetch_lengths() 函数

定义和用法

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

mysqli_fetch_lengths() 函数接受结果对象作为参数，检索给定结果的当前行中列的长度，并以数组的形式返回它们。

语法

mysqli_fetch_lengths($result);

参数

返回值

如果成功，PHP mysqli_fetch_lengths() 函数返回一个包含每一列（当前行）的长度/大小的整数数组；如果出错，则返回布尔值 FALSE。

PHP 版本

此函数首次引入于 PHP 5 版本，并在所有后续版本中均有效。

示例

以下示例演示了 mysqli_fetch_lengths() 函数（在过程式风格中）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
   $res = mysqli_query($con, "SELECT * FROM myplayers");

   //Lengths of the rows
   $row = mysqli_fetch_row($res);
   $lengths = mysqli_fetch_lengths($res);

   print_r($lengths);
   mysqli_free_result($res);

   mysqli_close($con);
?>

这将产生以下结果：

Table Created.....
Record Inserted.....
Array
(
    [0] => 1
    [1] => 6
    [2] => 6
    [3] => 5
    [4] => 5
)

示例

在面向对象风格中，此函数的语法为 $result->lengths; 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
   $res = $stmt->get_result();
   $row = $res->fetch_row();

   $len = $res ->lengths;
   print_r($len);

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

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

这将产生以下结果：

Table Created.....
Array
(
    [0] => 4
    [1] => 0
)

示例

为了使此函数检索长度，必须在使用 mysqli_fetch_row/array/object 方法获取行之后调用它，否则它将返回 false。

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

   mysqli_query($con, "CREATE TABLE data(ID INT, Name VARCHAR(255), Age INT)");
   mysqli_query($con, "INSERT INTO data values(1, 'Mohan', 25)");
   mysqli_query($con, "INSERT INTO data values(2, 'Syamala', 36)");
   print("Record Inserted.....\n");

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

   //Lengths of the rows
   $bool = $lengths = mysqli_fetch_lengths($res);

   if($bool){
      print("Lengths Retrieved");
   }else{
      print("Failed");
   }

   print_r($lengths);
   mysqli_free_result($res);

   mysqli_close($con);
?>

这将产生以下结果：

Record Inserted.....
Failed