getMessage();
    }

    for( $i = 0; $i < 10; $i++){
            $sql = "INSERT INTO `tbl_test` (id, name) VALUE (:id, :name)";
            $data = array(
                    ":id" => "",
                    ":name" => "user_$i"
            );
            $sth = $dbh->prepare($sql);
            $sth->execute($data);
    }

    $sql = "INSERT INTO `tbl_test` (id, name) VALUE (:id, :name)";
    $new_data = array(
            ":id" => "",
            ":name" => "user_new"
    );
    $sth = $dbh->prepare($sql);
    $sth->execute($new_data);
    $last_id = $dbh->lastInsertId();
    echo "last id: " . $last_id;

結(jié)果

last id: 11

getMessage();
    }

    for( $i = 0; $i < 10; $i++){
            $sql = "INSERT INTO `tbl_test` (id, name) VALUE (:id, :name)";
            $data = array(
                    ":id" => $i,
                    ":name" => "user_$i"
            );
            $sth = $dbh->prepare($sql);
            $sth->execute($data);
    }

    $sql = "INSERT INTO `tbl_test` (id, name) VALUE (:id, :name)";
    $new_data = array(
            ":id" => "",
            ":name" => "user_new"
    );
    $sth = $dbh->prepare($sql);
    $sth->execute($new_data);
    $last_id = $dbh->lastInsertId();
    echo "last id: " . $last_id;

結(jié)果

last id: 0

getMessage();
    }

    for( $i = 0; $i < 10; $i++){
            $sql = "INSERT INTO `tbl_test` (tbl_id, name) VALUE (:tbl_id, :name)";
            $data = array(
                    ":tbl_id" => $i,
                    ":name" => "user_$i"
            );
            $sth = $dbh->prepare($sql);
            $sth->execute($data);
    }

    $sql = "INSERT INTO `tbl_test` (tbl_id, name) VALUE (:tbl_id, :name)";
    $new_data = array(
            ":tbl_id" => "",
            ":name" => "user_new"
    );
    $sth = $dbh->prepare($sql);
    $sth->execute($new_data);
    $last_id = $dbh->lastInsertId();
    echo "last id: " . $last_id;

結(jié)果

last id: 11

getMessage();
    }

    for( $i = 0; $i < 10; $i++){
            $sql = "INSERT INTO `tbl_test` (tbl_id, name) VALUE (:tbl_id, :name)";
            $data = array(
                    ":tbl_id" => uniqid(),
                    ":name" => "user_$i"
            );
            $sth = $dbh->prepare($sql);
            $sth->execute($data);
    }

    $sql = "INSERT INTO `tbl_test` (tbl_id, name) VALUE (:tbl_id, :name)";
    $new_data = array(
            ":tbl_id" => uniqid(),
            ":name" => "user_new"
    );
    $sth = $dbh->prepare($sql);
    $sth->execute($new_data);
    $last_id = $dbh->lastInsertId();
    echo "last id: " . $last_id;

結(jié)果

last id: 0

可以看到，有些例子返回0，有些例子返回最新的ID。那么lastInsertId什么情況下會返回0呢？在網(wǎng)上搜了很多資料，并沒有發(fā)現(xiàn)想要的答案，翻開PHP源碼，發(fā)現(xiàn)函數(shù)last_insert_id的實現(xiàn)源碼是這樣的：

可以看到，函數(shù)返回的id的值是調(diào)用mysql api中的mysql_insert_id函數(shù)返回的值。

翻開mysql手冊，在這里找到這一段：

mysql_insert_id() returns the value stored into an AUTO_INCREMENT column, whether that value is automatically generated by storing NULL or 0 or was specified as an explicit value. LAST_INSERT_ID() returns only automatically generated AUTO_INCREMENT values. If you store an explicit value other than NULL or 0, it does not affect the value returned by LAST_INSERT_ID().

從手冊的描述可以知道，mysql_insert_id函數(shù)返回的是儲存在有AUTO_INCREMENT約束的字段的值，如果表中的字段不使用AUTO_INCREMENT約束或者使用自己生成的唯一值插入，那么該函數(shù)不會返回你所存儲的值，而是返回NULL或0。因此，在沒有使用AUTO_INCREMENT約束的表中，或者ID是自己生成的唯一ID，lastInsertId函數(shù)返回的都是0。

那么，有沒有另一種方法可以幫助我們判斷程序執(zhí)行插入是否成功呢？答案是有的。在PDO執(zhí)行了excecute之后，調(diào)用PDO實例的rowCount函數(shù)可以得到執(zhí)行之后的影響行數(shù)，如果結(jié)果非0，那么說明數(shù)據(jù)庫插入操作執(zhí)行成功了。下面這個解決方案的一小段demo：

$sql = "INSERT INTO `tbl_test` (tbl_id, name) VALUE (:tbl_id, :name)";
$new_data = array(
        ":tbl_id" => uniqid(),
        ":name" => "user_another"
);
$sth = $dbh->prepare($sql);
$sth->execute($new_data);
$row_count = $sth->rowCount();
if( $row_count ){
    echo "execute success";
} else{
    echo "execute failed";
}

本文探討一個問題出現(xiàn)的原因和一個解決方案，由于個人水平有限，如有更好的方法或者其他建議和批評，歡迎指出。

注：本文使用的是PHP5.4.15，MySQL5.5.41。