PHP PDOStatement::fetch讲解
PDOStatement::fetch
PDOStatement::fetch — 从结果集中获取下一行(PHP 5 >= 5.1.0, PECL pdo >= 0.1.0)
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。
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，缺省为 PDO::ATTR_DEFAULT_FETCH_MODE 的值 （默认为 PDO::FETCH_BOTH ）。
_PDO::FETCHASSOC ：返回一个索引为结果集列名的数组 _PDO::FETCHBOTH （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::FETCHBOUND ：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::FETCHCLASS ：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::FETCHCLASSTYPE ），则类名由第一列的值决定 _PDO::FETCHINTO ：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::FETCHLAZY ：结合使用 _PDO::FETCHBOTH 和 _PDO::FETCHOBJ ，创建供用来访问的对象变量名 _PDO::FETCHNUM ：返回一个索引为以0开始的结果集列号的数组 _PDO::FETCHOBJ ：返回一个属性名对应结果集列名的匿名对象cursor_orientation
offset
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 。
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\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 $result->NAME;
print("\n");
?>
以上实例会输出：
PDO::FETCH_ASSOC: Return next row as an array indexed by column name
Array
(
[NAME] => apple
[COLOUR] => red
)
PDO::FETCH_BOTH: Return next row as an array indexed by both column name and number
Array
(
[NAME] => banana
[0] => banana
[COLOUR] => yellow
[1] => yellow
)
PDO::FETCH_LAZY: Return next row as an anonymous object with column names as properties
PDORow Object
(
[NAME] => orange
[COLOUR] => orange
)
PDO::FETCH_OBJ: Return next row as an anonymous object with column names as properties
kiwi
使用一个可滚动游标获取行
<?php
function readDataForwards($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] . "\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 5
16 0 5
19 20 10
Reading backwards:
19 20 10
16 0 5
21 10 5
总结
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