PHP调用常量使用变量

Question

//include.php
    define('OPTION_0', 'Essence of population');
    define('OPTION_1', 'Passport request/extend');
    define('OPTION_2', 'Request logging concession');

//form.php
    <select name="sort">
        <option value="0"><?php echo(O_0) ?></option>
        <option value="1"><?php echo(O_1) ?></option>
        <option value="2"><?php echo(O_2 ?></option>
    </select>


//show.php
    extract($_POST);                    //The variable $sort has the value 1,2 or 3
    echo("This is your choice");
    echo(OPTION_ . $sort);              //I want to use de constant e.g. OPTION_2

I want to echo the value of the matching constant. So when I select the second value in form.php it gives $sort the value of 1 now I want to use the constants OPTION_1.

Can someone help me?

Answer 1

Just use constant() function:

echo constant('OPTION_' . $sort);

constant() is useful if you need to retrieve the value of a constant, but do not know its name. Ie it is stored in a variable or returned by a function.