PHP 中的数组而不是单个项目

Question

虽然查询输出应该是单个单元格，但这给了我一个包含两个项目的数组，这可能很明显，但对像我这样的初学者来说不是这样

$db = new PDO("mysql:host={$host};dbname={$dbname};charset=utf8", $username, $password, $options); 
$options = array(PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES utf8'); 

function dbFetch($db,$query)
    {
        $stmt = $db->prepare($query); 
        $stmt->execute(); 
        return $stmt->fetch();
    }

$query = " 
SELECT
Name
FROM Players WHERE PlayerID='21'"; 
$rows = dbFetch($db,$query);
var_dump($rows);

输出：

array(2) { ["Name"]=> string(6) "PLAYERNAME" [0]=> string(6) "PLAYERNAME" }

它首先作为关联重复输出，然后作为数字重复输出。

Answer 1

请尝试使用 PDOStatement::fetchColumn()。它将 return 第一条记录的第一列。

function dbFetch($db,$query)
{
    $stmt = $db->prepare($query); 
    $stmt->execute(); 
    return $stmt->fetchColumn(0);
}

此外，我敢打赌您不是在搜索“21”，而是在搜索一个变量。在那种情况下，你最好使用 prepared statements，并像这样修改你的代码：

$db = new PDO("mysql:host={$host};dbname={$dbname};charset=utf8", $username, $password, $options); 
$options = array(PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES utf8'); 
function dbFetch($db,$query,$params=[])
{
    $stmt = $db->prepare($query); 
    $stmt->execute($params); 
    return $stmt->fetch();
}

$query = " 
SELECT
Name
FROM Players WHERE PlayerID=?";
$params = array("your user id"); 
$rows = dbFetch($db,$query,$params);
var_dump($rows);

Answer 2

可能是由于抓取样式。

根据 php 手册：

public mixed PDOStatement::fetch ([ int $fetch_style [, int $cursor_orientation = PDO::FETCH_ORI_NEXT [, int $cursor_offset = 0 ]]] ) Fetches a row from a result set associated with a PDOStatement object. The fetch_style parameter determines how PDO returns the row.

fetch_style Controls how the next row will be returned to the caller. This value must be one of the PDO::FETCH_* constants, defaulting to value of PDO::ATTR_DEFAULT_FETCH_MODE (which defaults to PDO::FETCH_BOTH).

PDO::FETCH_ASSOC: returns an array indexed by column name as returned in your result set

PDO::FETCH_BOTH (default): returns an array indexed by both column name and 0-indexed column number as returned in your result set

PDO::FETCH_BOUND: returns TRUE and assigns the values of the columns in your result set to the PHP variables to which they were bound with the PDOStatement::bindColumn() method

PDO::FETCH_CLASS: returns a new instance of the requested class, mapping the columns of the result set to named properties in the class, and calling the constructor afterwards, unless PDO::FETCH_PROPS_LATE is also given. If fetch_style includes PDO::FETCH_CLASSTYPE (e.g. PDO::FETCH_CLASS | PDO::FETCH_CLASSTYPE) then the name of the class is determined from a value of the first column.

PDO::FETCH_INTO: updates an existing instance of the requested class, mapping the columns of the result set to named properties in the class

PDO::FETCH_LAZY: combines PDO::FETCH_BOTH and PDO::FETCH_OBJ, creating the object variable names as they are accessed

PDO::FETCH_NAMED: returns an array with the same form as PDO::FETCH_ASSOC, except that if there are multiple columns with the same name, the value referred to by that key will be an array of all the values in the row that had that column name

PDO::FETCH_NUM: returns an array indexed by column number as returned in your result set, starting at column 0

PDO::FETCH_OBJ: returns an anonymous object with property names that correspond to the column names returned in your result set

PDO::FETCH_PROPS_LATE: when used with PDO::FETCH_CLASS, the constructor of the class is called before the properties are assigned from the respective column values.

PHP 中的数组而不是单个项目

Array instead of a single item in PHP

php

mysql

pdo

fetch