php Declare a variable by type held in a string

Question

I am trying to declare an object by the value held in a string. So if a string holds 'Class1' i want to declare it by type Class1.

Something like this

$CT = "Class1";
if (class_exists($CT))
    $MyClass = new Type($CT);

I can do something like the following, but would rather do it as above if possible.

if (isset($_GET["CT"]))
    $CT = $_GET["CT"];
else
    $CT = "Class1";

echo "CT = " . $CT . "<br>";

switch ($CT)
{
    case "Class1":
        $MyClass = new Class1;
        break;

    case "Class2":
        $MyClass = new Class2;
        break;

    default:
        $MyClass = new Class1;
    
}

echo $MyClass->Result();

class Class1
{
    function Result()
    {
        return "I am Class 1";
    }
}

class Class2
{
    function Result()
    {
        return "I am Class 2";
    }
}

Not sure what that Type thing should be, but $MyClass = new $CT; — user8034901
– user8034901, Commented Feb 20, 2021 at 15:07

Enrico Dias · Accepted Answer · 2021-02-20 15:07:41Z

3

You can use variables after the new keyword:

$CT = "Class1";
if (class_exists($CT))
    $MyClass = new $CT();

answered Feb 20, 2021 at 15:07

Enrico Dias

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Comments

Dev Man · Accepted Answer · 2021-02-20 15:08:57Z

0

You can most assuredly create a class instance by its name alone, so your code would be

<?php

if (isset($_GET["CT"]))
    $CT = $_GET["CT"];
else
    $CT = "Class1";

echo "CT = " . $CT . "<br>";

$instance = new $CT();

echo $instance->Result();

class Class1
{
    function Result()
    {
        return "I am Class 1";
    }
}

class Class2
{
    function Result()
    {
        return "I am Class 2";
    }
}

See it in action here

answered Feb 20, 2021 at 15:08

Dev Man

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