Create an object from a string variable in PHP

Create an object from a string variable in PHP

In PHP, objects can be created from string variables. It provides a very convenient way for you to define rules in text and handle requests dynamically. In this post, we show you how to do it.

Create an object from a string variable

Supposed we have a class called Rectangle, it is for a rectangle shape and it calculates its area.

class Rectangle
    private $length;
    private $width;

    public function setLength($l) {
        $this->length = $l;

    public function setWidth($w) {
        $this->width = $w;

    public function setLengthWidth($l, $w) {
         $this->length = $l;
         $this->width = $w;

    public function getArea() {
        return $this->length * $this->width;


You can use a string variable to create the Rectangle object like this:

$className = "Rectangle";
$class = new $className();

Also, a function in a class can be called by using a string variable. If you want to call the function setLength() and setWidth() in the class Rectangle, you can do as follows:

$length = 10;
$width = 3;

$setLength = "setLength";
$setWidth = "setWidth";


Or, you can just use a string in the {} to call a function like this:

$class->{"setLengthWidth"}($length, $width);

To calculate the Rectangle's area, the function getArea() can be called as follows:

echo "The area is: " . $class->{"getArea"}(); // The area is: 30

Create rules and call functions dynamically

Here, we show you an example how to call functions dynamically based on the request.


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