如何在SQL查询中插入PHP常量? [英] How do you insert a PHP constant into a SQL query?

问题描述

我有一个PHP文件，其数据库配置设置定义为常量，例如:

I have a PHP file with my database configuration settings defined as constants, for example:

<?php

define(DB_HOST,"localhost");
define(DB_USERNAME,"root");
define(DB_PASSWORD,"password");
define(DB_NAME,"db_users");
define(DB_TABLE_1,"table_1");
define(DB_TABLE_2,"table_2);

?>

很明显，每当我想连接到数据库时，我都会包含上述文件.但是，当我将表定义常量插入SQL查询中时(见下文)，它似乎不起作用.我需要适当地对常量进行转义还是以某种方式将其连接起来?

I obviously include the above file whenever I want to connect to my database..However, when I go to insert the table definition constants into the SQL query (see below) it doesn't seem to work. Do I need to properly escape the constant or concatenate it in some way?

$query = "SELECT users FROM DB_TABLE_1";

推荐答案

您将不得不使用字符串连接(任何形式).

You'll have to use string concatenation (of any sort).

$query = "SELECT users FROM " . DB_TABLE_1;

常量将不会像变量那样插入到字符串中.

constants will not interpolate into a string as variables can.

一种骇人听闻的选择是使用变量函数:

One hackish alternative is to use a variable function:

$const = 'constant';
$query = "SELECT users FROM {$const('DB_TABLE_1')}";

这将执行constant()函数并返回常量的值，但是，仅出于可读性考虑，这通常不是一个好主意.

which'll execute the constant() function and return the constant's value, but that's generally not a good idea, if only for legibility's sake.

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