PDOStatement::fetch — 从结果集中获取下一行(PHP 5 >= 5.1.0, PECL pdo >= 0.1.0)
mixed PDOStatement::fetch ([ int $fetch_style [, int $cursor_orientation = PDO::FETCH_ORI_NEXT [, int $cursor_offset = 0 ]]] )
从一个 PDOStatement 对象相关的结果集中获取下一行。fetch_style 参数决定 POD 如何返回行。
fetch_style
控制下一行如何返回给调用者。此值必须是 PDO::FETCH_* 系列常量中的一个，缺省为 PDO::ATTR_DEFAULT_FETCH_MODE 的值 （默认为 PDO::FETCH_BOTH ）。
PDO::FETCH_ASSOC：返回一个索引为结果集列名的数组
PDO::FETCH_BOTH（默认）：返回一个索引为结果集列名和以0开始的列号的数组
PDO::FETCH_BOUND：返回 TRUE，并分配结果集中的列值给PDOStatement::bindColumn() 方法绑定的 PHP 变量。
PDO::FETCH_CLASS：返回一个请求类的新实例，映射结果集中的列名到类中对应的属性名。如果 fetch_style包含 PDO::FETCH_CLASSTYPE（例如：PDO::FETCH_CLASS | PDO::FETCH_CLASSTYPE），则类名由第一列的值决定
PDO::FETCH_INTO：更新一个被请求类已存在的实例，映射结果集中的列到类中命名的属性
PDO::FETCH_LAZY：结合使用 PDO::FETCH_BOTH和 PDO::FETCH_OBJ，创建供用来访问的对象变量名
PDO::FETCH_NUM：返回一个索引为以0开始的结果集列号的数组
PDO::FETCH_OBJ：返回一个属性名对应结果集列名的匿名对象
cursor_orientation 对于 一个 PDOStatement 对象表示的可滚动游标，该值决定了哪一行将被返回给调用者。此值必须是 PDO::FETCH_ORI_* 系列常量中的一个，默认为 PDO::FETCH_ORI_NEXT。要想让 PDOStatement 对象使用可滚动游标，必须在用 PDO::prepare() 预处理SQL语句时，设置 PDO::ATTR_CURSOR 属性为 PDO::CURSOR_SCROLL。
offset对于一个 cursor_orientation 参数设置为 PDO::FETCH_ORI_ABS 的PDOStatement 对象代表的可滚动游标，此值指定结果集中想要获取行的绝对行号。对于一个 cursor_orientation 参数设置为 PDO::FETCH_ORI_REL 的PDOStatement 对象代表的可滚动游标，此值指定想要获取行相对于调用 PDOStatement::fetch() 前游标的位置
此函数（方法）成功时返回的值依赖于提取类型。在所有情况下，失败都返回 FALSE 。
<?php$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 namen");$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 numbern");$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 propertiesn");$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 propertiesn");$result = $sth->fetch(PDO::FETCH_OBJ);print $result->NAME;print("n");?>以上实例会输出：
PDO::FETCH_ASSOC: Return next row as an array indexed by column nameArray( [NAME] => apple [COLOUR] => red)PDO::FETCH_BOTH: Return next row as an array indexed by both column name and numberArray( [NAME] => banana [0] => banana [COLOUR] => yellow [1] => yellow)PDO::FETCH_LAZY: Return next row as an anonymous object with column names as propertiesPDORow Object( [NAME] => orange [COLOUR] => orange)PDO::FETCH_OBJ: Return next row as an anonymous object with column names as propertieskiwi
<?phpfunction readDataForwards($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); do { $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 10 516 0 519 20 10Reading backwards:19 20 1016 0 521 10 5