StringTemplate.php

<?php
class StringTemplate
{
    /**
     * The input / base string template to use.
     *
     * @param string|null
     */
    protected $template = null;

    /**
     * The values to replace in the input / base string.
     *
     * @param array
     */
    protected $replace = [];

    /**
     * Creates a new StringTemplate instance.
     *
     * @param string $template The input / base string.
     * @param string ...$replace The values to replace in the $template string.
     * @return void
     */
    public function __construct(string $template, string ...$replace)
    {
        $this->template = $template;
        $this->replace = $replace;
    }

    /**
     * Checks if $key is given in $replace
     *
     * @param mixed $key
     * @return bool
     */
    private function has($key) : boolean
    {
        return array_key_exists($key, $this->replace);
    }

    /**
     * Outputs the result
     *
     * @return string|null
     */
    public function output() : ?string
    {
        $output = $this->template;

        if(count($this->replace) > 0)
        {
            foreach($this->replace as $key => $value)
            {
                $output = str_replace('$(' . $key . ')', $value, $output);
            }
        }

        return $output;
    }

    /**
     * Outputs the class as a string.
     *
     * @see output()
     * @return string
     */
    public function __toString() : string
    {
        return $this->output();
    }
}