Learn how to register a Twig extension manually in a symfony 4 project without the autowire feature.

If the autowire feature of your Symfony 4 project is enabled, twig extensions are automatically registered in your app if the extension extends the AbstractExtension class and they're stored on the app/src/Twig directory. However, in some project this feature may disabled for reasons that are not of our interest. If that's your case, you may need to know how to register such extension in Symfony 4.

In this tutorial, we'll explain you how to register a Twig extension in your project easily without the autowire feature.

1. Create extension

As first step, you will need to have a Twig extension created, you can either use your own extension or use an example extension. In this case, in our example extension we'll add a filter and a function to our proyect (just remove them of the class if you are using the following example). The class will use the App\Twig namespace and extends the AbstractExtension:


// app/src/Twig/AppExtension.php
namespace App\Twig;

use Twig\Extension\AbstractExtension;
use Twig\TwigFilter;
use Twig\TwigFunction;

class AppExtension extends AbstractExtension
    public function getFilters()
        return [
            new TwigFilter('minifyVal', [$this, 'minifyVal']),
    public function getFunctions()
        return [
            new TwigFunction('is_mobile', [$this, 'is_mobile']),
     * Verificar si el dispositivo es un mobil desde php
     * @return boolean
    public function is_mobile(){
        $useragent = $_SERVER['HTTP_USER_AGENT'];
        if(preg_match('/(android|bb\d+|meego).+mobile|avantgo|bada\/|blackberry|blazer|compal|elaine|fennec|hiptop|iemobile|ip(hone|od)|iris|kindle|lge |maemo|midp|mmp|mobile.+firefox|netfront|opera m(ob|in)i|palm( os)?|phone|p(ixi|re)\/|plucker|pocket|psp|series(4|6)0|symbian|treo|up\.(browser|link)|vodafone|wap|windows ce|xda|xiino/i',$useragent)||preg_match('/1207|6310|6590|3gso|4thp|50[1-6]i|770s|802s|a wa|abac|ac(er|oo|s\-)|ai(ko|rn)|al(av|ca|co)|amoi|an(ex|ny|yw)|aptu|ar(ch|go)|as(te|us)|attw|au(di|\-m|r |s )|avan|be(ck|ll|nq)|bi(lb|rd)|bl(ac|az)|br(e|v)w|bumb|bw\-(n|u)|c55\/|capi|ccwa|cdm\-|cell|chtm|cldc|cmd\-|co(mp|nd)|craw|da(it|ll|ng)|dbte|dc\-s|devi|dica|dmob|do(c|p)o|ds(12|\-d)|el(49|ai)|em(l2|ul)|er(ic|k0)|esl8|ez([4-7]0|os|wa|ze)|fetc|fly(\-|_)|g1 u|g560|gene|gf\-5|g\-mo|go(\.w|od)|gr(ad|un)|haie|hcit|hd\-(m|p|t)|hei\-|hi(pt|ta)|hp( i|ip)|hs\-c|ht(c(\-| |_|a|g|p|s|t)|tp)|hu(aw|tc)|i\-(20|go|ma)|i230|iac( |\-|\/)|ibro|idea|ig01|ikom|im1k|inno|ipaq|iris|ja(t|v)a|jbro|jemu|jigs|kddi|keji|kgt( |\/)|klon|kpt |kwc\-|kyo(c|k)|le(no|xi)|lg( g|\/(k|l|u)|50|54|\-[a-w])|libw|lynx|m1\-w|m3ga|m50\/|ma(te|ui|xo)|mc(01|21|ca)|m\-cr|me(rc|ri)|mi(o8|oa|ts)|mmef|mo(01|02|bi|de|do|t(\-| |o|v)|zz)|mt(50|p1|v )|mwbp|mywa|n10[0-2]|n20[2-3]|n30(0|2)|n50(0|2|5)|n7(0(0|1)|10)|ne((c|m)\-|on|tf|wf|wg|wt)|nok(6|i)|nzph|o2im|op(ti|wv)|oran|owg1|p800|pan(a|d|t)|pdxg|pg(13|\-([1-8]|c))|phil|pire|pl(ay|uc)|pn\-2|po(ck|rt|se)|prox|psio|pt\-g|qa\-a|qc(07|12|21|32|60|\-[2-7]|i\-)|qtek|r380|r600|raks|rim9|ro(ve|zo)|s55\/|sa(ge|ma|mm|ms|ny|va)|sc(01|h\-|oo|p\-)|sdk\/|se(c(\-|0|1)|47|mc|nd|ri)|sgh\-|shar|sie(\-|m)|sk\-0|sl(45|id)|sm(al|ar|b3|it|t5)|so(ft|ny)|sp(01|h\-|v\-|v )|sy(01|mb)|t2(18|50)|t6(00|10|18)|ta(gt|lk)|tcl\-|tdg\-|tel(i|m)|tim\-|t\-mo|to(pl|sh)|ts(70|m\-|m3|m5)|tx\-9|up(\.b|g1|si)|utst|v400|v750|veri|vi(rg|te)|vk(40|5[0-3]|\-v)|vm40|voda|vulc|vx(52|53|60|61|70|80|81|83|85|98)|w3c(\-| )|webc|whit|wi(g |nc|nw)|wmlb|wonu|x700|yas\-|your|zeto|zte\-/i',substr($useragent,0,4))){
            return true;
        return false;

     * Allows you to determine the most readable format of a number of bytes.
     * @param type $n
     * @param type $precision
     * @return type
    public function minifyVal($n, $precision = 1 ){
	if ($n < 900) {
            $n_format = number_format($n, $precision);
            $suffix = '';
	} else if ($n < 900000) {
            $n_format = number_format($n / 1000, $precision);
            $suffix = 'K';
	} else if ($n < 900000000) {
            $n_format = number_format($n / 1000000, $precision);
            $suffix = 'M';
	} else if ($n < 900000000000) {
            $n_format = number_format($n / 1000000000, $precision);
            $suffix = 'B';
	} else {
            $n_format = number_format($n / 1000000000000, $precision);
            $suffix = 'T';
	if ( $precision > 0 ) {
            $dotzero = '.' . str_repeat( '0', $precision );
            $n_format = str_replace( $dotzero, '', $n_format );
	return $n_format . $suffix;

2. Register extension

Once the extension file is in the mentioned directory, proceed to register it in the services.yaml file of your project like this (under the services block):

# app/config/services.yaml
        class: App\Twig\AppExtension
        public: false
            - { name: twig.extension } 

If you are in the dev environment, once you reload your app, the extension will be loaded and immediately available (the minifiVal filter and is_mobile function).

Happy coding !

Senior Software Engineer at Software Medico. Interested in programming since he was 14 years old, Carlos is a self-taught programmer and founder and author of most of the articles at Our Code World.