Interfaces

Interfaces in PHP serve as a blueprint for designing classes. They ensure that a class adheres to a certain contract, all without defining how those methods should function. As PHP is not a strictly typed language, interfaces can be particularly useful in large codebases to maintain continuity and predictability. For example, in PHP, an interface 'iTemplate' could be defined with methods 'setVariable' and 'getHtml'. Any class that implements this interface must define these methods.

Here is a snippet:

interface iTemplate {
    public function setVariable($name, $var);
    public function getHtml($template); 
}

class Template implements iTemplate {
    private $vars = array();

    public function setVariable($name, $var) {
        $this->vars[$name] = $var;
    }

    public function getHtml($template) {
        foreach($this->vars as $name => $value) {
            $template = str_replace('{' . $name . '}', $value, $template);
        }
        return $template;
    }
}