PHP mysqli_result $lengths 属性

 PHP MySQLi 函数

PHP mysqli_result::$lengths / mysqli_fetch_lengths() 函数返回一个数组，其中包含结果集中的当前行。

语法

//面向对象风格
$mysqli_result->lengths;

//面向过程风格
mysqli_fetch_lengths(result)

参数

返回值

返回表示每列大小的整数数组（不包括任何终止空字符）。如果发生错误，则返回 false。

mysqli_fetch_lengths() 仅对结果集的当前行有效。如果在调用 mysqli_fetch_row/array/object 之前或检索结果中的所有行之后调用，则返回 false。

示例:面向对象风格

下面的示例显示了 的用法mysqli_result::$lengths 属性。

<?php
//建立与数据库的连接
$mysqli = new mysqli("localhost", "user", "password", "database");
if ($mysqli->connect_errno) {
  echo "Failed to connect to MySQL: ". $mysqli->connect_error;
  exit();
}

//从数据库获取查询结果
$sql = "SELECT EmpId, Name, Age FROM Employee ORDER BY Age";

if ($result = $mysqli->query($sql)) {

  //从结果集中取出一行数据
  $row = $result->fetch_row();

  //显示列长度
  foreach ($result->lengths as $i => $val) {
    printf("Field %2d has Length %2d\n", $i+1, $val);
  }

  //释放与结果相关的内存
  $result->close();
}

//关闭连接
$mysqli->close();
?>

上述代码的输出将类似于:

Field 1 has Length 4
Field 2 has Length 12
Field 3 has Length 3

示例:面向过程风格

下面的示例显示了 mysqli_fetch_lengths() 函数的用法。

<?php
//建立与数据库的连接
$mysqli = mysqli_connect("localhost", "user", "password", "database");
if (mysqli_connect_errno()) {
  echo "Failed to connect to MySQL: ". mysqli_connect_error();
  exit();
}

//从数据库获取查询结果
$sql = "SELECT EmpId, Name, Age FROM Employee ORDER BY Age";

if ($result = mysqli_query($mysqli, $sql)) {

  //从结果集中取出一行数据
  $row = mysqli_fetch_row($result);

  //显示列长度
  foreach (mysqli_fetch_lengths($result) as $i => $val) {
    printf("Field %2d has Length %2d\n", $i+1, $val);
  }

  //释放与结果相关的内存
  mysqli_free_result($result);
}

//关闭连接
mysqli_close($mysqli);
?>

上述代码的输出将类似于:

Field 1 has Length 4
Field 2 has Length 12
Field 3 has Length 3