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。
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
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 。
用不同的提取方式获取行
$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\n");
$result = $sth->fetch(PDO::FETCH_ASSOC);
print_r($result);
print("\n");
print("PDO::FETCH_BOTH: ");
print("Return next row as an array indexed by both column name and number\n");
$result = $sth->fetch(PDO::FETCH_BOTH);
print_r($result);
print("\n");
print("PDO::FETCH_LAZY: ");
print("Return next row as an anonymous object with column names as properties\n");
$result = $sth->fetch(PDO::FETCH_LAZY);
print_r($result);
print("\n");
print("PDO::FETCH_OBJ: ");
print("Return next row as an anonymous object with column names as properties\n");
$result = $sth->fetch(PDO::FETCH_OBJ);
print $result->NAME;
print("\n");
以上实例会输出：
PDO::FETCH_ASSOC: Return next row as an array indexed by column name
Array
[NAME] => apple
[COLOUR] => red
PDO::FETCH_BOTH: Return next row as an array indexed by both column name and number
Array
[NAME] => banana
[0] => banana
[COLOUR] => yellow
[1] => yellow
PDO::FETCH_LAZY: Return next row as an anonymous object with column names as properties
PDORow Object
[NAME] => orange
[COLOUR] => orange
PDO::FETCH_OBJ: Return next row as an anonymous object with column names as properties
使用一个可滚动游标获取行
function readDataForwards($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] . "\t" . $row[1] . "\t" . $row[2] . "\n";
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);
$data = $row[0] . "\t" . $row[1] . "\t" . $row[2] . "\n";
print $data;
} while ($row = $stmt->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_PRIOR));
$stmt = null;
catch (PDOException $e) {
print $e->getMessage();
print "Reading forwards:\n";
readDataForwards($conn);
print "Reading backwards:\n";
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
PHP PDO 参考手册
