PDOStatement::fetch

PDOStatement::fetch — 从结果集中获取下一行(PHP 5 >= 5.1.0, PECL pdo >= 0.1.0)

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说明

语法

mixed PDOStatement::fetch ([ int $fetch_style [, int $cursor_orientation = PDO::FETCH_ORI_NEXT [, int $cursor_offset = 0 ]]] )

从一个 PDOStatement 对象相关的结果集中获取下一行。fetch_style 参数决定 POD 如何返回行。高佣联盟 www.cgewang.com

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参数

fetch_style

控制下一行如何返回给调用者。此值必须是 PDO::FETCH_* 系列常量中的一个，默认为 PDO::ATTR_DEFAULT_FETCH_MODE 的值 （默认为 PDO::FETCH_BOTH ）。

• PDO::FETCH_ASSOC：返回一个索引为结果集列名的数组

• PDO::FETCH_BOTH（默认）：返回一个索引为结果集列名和以0开始的列号的数组

• PDO::FETCH_BOUND：返回 TRUE ，并分配结果集中的列值给PDOStatement::bindColumn() 方法绑定的 PHP 变量。

• PDO::FETCH_CLASS：返回一个请求类的新实例，映射结果集中的列名到类中对应的属性名。如果 fetch_style 包含 PDO::FETCH_CLASSTYPE（例如：PDO::FETCH_CLASS | PDO::FETCH_CLASSTYPE），则类名由第一列的值决定

• PDO::FETCH_INTO：更新一个被请求类已存在的实例，映射结果集中的列到类中命名的属性

• PDO::FETCH_LAZY：结合使用 PDO::FETCH_BOTH 和 PDO::FETCH_OBJ，创建供用来访问的对象变量名

• PDO::FETCH_NUM：返回一个索引为以0开始的结果集列号的数组

• PDO::FETCH_OBJ：返回一个属性名对应结果集列名的匿名对象

cursor_orientation
对于 一个 PDOStatement 对象表示的可滚动游标，该值决定了哪一行将被返回给调用者。此值必须是 PDO::FETCH_ORI_* 系列常量中的一个，默认为 PDO::FETCH_ORI_NEXT。要想让 PDOStatement 对象使用可滚动游标，必须在用 PDO::prepare() 预处理SQL语句时，设置 PDO::ATTR_CURSOR 属性为 PDO::CURSOR_SCROLL。

offset
对于一个 cursor_orientation 参数设置为 PDO::FETCH_ORI_ABS 的PDOStatement 对象代表的可滚动游标，此值指定结果集中想要获取行的绝对行号。 
对于一个 cursor_orientation 参数设置为 PDO::FETCH_ORI_REL 的PDOStatement 对象代表的可滚动游标，此值指定想要获取行相对于调用 PDOStatement::fetch() 前游标的位置

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返回值

此函数（方法）成功时返回的值依赖于提取类型。在所有情况下，失败都返回 FALSE 。

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实例

用不同的提取方式获取行

<?php
$sth = $dbh->prepare("SELECT name, colour FROM fruit");
$sth->execute();

/* 运用 PDOStatement::fetch 风格 */
print("PDO::FETCH_ASSOC: ");
print("Return next row as an array indexed by column name
");
$result = $sth->fetch(PDO::FETCH_ASSOC);
print_r($result);
print("
");

print("PDO::FETCH_BOTH: ");
print("Return next row as an array indexed by both column name and number
");
$result = $sth->fetch(PDO::FETCH_BOTH);
print_r($result);
print("
");

print("PDO::FETCH_LAZY: ");
print("Return next row as an anonymous object with column names as properties
");
$result = $sth->fetch(PDO::FETCH_LAZY);
print_r($result);
print("
");

print("PDO::FETCH_OBJ: ");
print("Return next row as an anonymous object with column names as properties
");
$result = $sth->fetch(PDO::FETCH_OBJ);
print $result->NAME;
print("
");
?>

以上实例会输出：

PDO::FETCH_ASSOC: Return next row as an array indexed by column name
Array
(
    [NAME] => apple
    [COLOUR] => red
)

PDO::FETCH_BOTH: Return next row as an array indexed by both column name and number
Array
(
    [NAME] => banana
    [0] => banana
    [COLOUR] => yellow
    [1] => yellow
)

PDO::FETCH_LAZY: Return next row as an anonymous object with column names as properties
PDORow Object
(
    [NAME] => orange
    [COLOUR] => orange
)

PDO::FETCH_OBJ: Return next row as an anonymous object with column names as properties
kiwi

使用一个可滚动游标获取行

<?php
function readDataForwards($dbh) {
  $sql = 'SELECT hand, won, bet FROM mynumbers ORDER BY BET';
  try {
    $stmt = $dbh->prepare($sql, array(PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL));
    $stmt->execute();
    while ($row = $stmt->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_NEXT)) {
      $data = $row[0] . "	" . $row[1] . "	" . $row[2] . "
";
      print $data;
    }
    $stmt = null;
  }
  catch (PDOException $e) {
    print $e->getMessage();
  }
}
function readDataBackwards($dbh) {
  $sql = 'SELECT hand, won, bet FROM mynumbers ORDER BY bet';
  try {
    $stmt = $dbh->prepare($sql, array(PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL));
    $stmt->execute();
    $row = $stmt->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_LAST);
    do {
      $data = $row[0] . "	" . $row[1] . "	" . $row[2] . "
";
      print $data;
    } while ($row = $stmt->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_PRIOR));
    $stmt = null;
  }
  catch (PDOException $e) {
    print $e->getMessage();
  }
}

print "Reading forwards:
";
readDataForwards($conn);

print "Reading backwards:
";
readDataBackwards($conn);
?>

以上实例会输出：

Reading forwards:
21    10    5
16    0     5
19    20    10

Reading backwards:
19    20    10
16    0     5
21    10    5