What is `HtmlString` used for in Laravel?

Question

This class: HtmlString

<?php

namespace Illuminate\Support;

use Illuminate\Contracts\Support\Htmlable;

class HtmlString implements Htmlable
{
    /**
     * The HTML string.
     *
     * @var string
     */
    protected $html;

    /**
     * Create a new HTML string instance.
     *
     * @param  string  $html
     * @return void
     */
    public function __construct($html)
    {
        $this->html = $html;
    }

    /**
     * Get the HTML string.
     *
     * @return string
     */
    public function toHtml()
    {
        return $this->html;
    }

    /**
     * Get the HTML string.
     *
     * @return string
     */
    public function __toString()
    {
        return $this->toHtml();
    }
}

use:

    function csrf_field()
    {
        return new HtmlString('<input type="hidden" name="_token" value="'.csrf_token().'">');
    }

It does nothing but "construct" an string and return the string itself!

Can anyone explain it? Thanks a lot :)

Answer 1

Since it implements an interface (Htmlable), other methods can potentially check whether a string it's been given should be treated as HTML or not.

It's not used that much, but for instance in Illuminate/Support/helpers.php:519:

if (! function_exists('e')) {
    /**
     * Escape HTML special characters in a string.
     *
     * @param  \Illuminate\Contracts\Support\Htmlable|string  $value
     * @return string
     */
    function e($value)
    {
        if ($value instanceof Htmlable) {
            return $value->toHtml();
        }

        return htmlspecialchars($value, ENT_QUOTES, 'UTF-8', false);
    }
}

Here, you can see that if the $value adhers to the Htmlable interface, it can be printed right away. Otherwise, the string is printed in escaped form.