How do you insert a PHP constant into a SQL query?

Question

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

Answer 1

Just put it outside the quotes and it should work fine:

$query = "SELECT users FROM ".DB_TABLE_1;

Answer 2

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

$query = "SELECT users FROM " . DB_TABLE_1;

constants will not interpolate into a string as variables can.

One hackish alternative is to use a variable function:

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

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.

Answer 3

I think this is easier:

$query = "SELECT users FROM '.DB_TABLE_1.'";

when using multiple tables:

$query = "SELECT TB_1.users, TB_2.names FROM '.TB_1.'
          INNER JOIN '.TB_2.' 
          ON x=y";

Also, this is better:

define("DB_HOST","localhost");

Answer 4

I've found two ways.

1.-

define("VALUE1", "someValue");
$query = "SELECT * FROM TABLE WHERE `Column` /*=" . VALUE1 . "*/";

2.-

define("VALUE1", "someValue");
define("VALUE2", "otherValue");
$query = "INSERT INTO TABLE (`Column1`, `Column2`) VALUES (" . VALUE1 . ", " . VALUE2 . ")";

The backticks (``) I use because I'm using phpmyadmin, you might not need them.