Mengapa Composer tidak diperbarui?

Saya menggunakan Ubuntu 16.04 LTS amd64. Saya telah menginstal LAMP (php5.6, apache2, mysql) dan Composer. Saya mengunduh proyek laravel saya dari github. Saya ingin memperbarui Komposer untuk memulai server lokal php artisan serve. Tetapi ketika saya ingin menjalankan localhost, terminal mengatakan:

heartprogrammer@heartprogrammer-desktop:/var/www/kstu$ php artisan serve
PHP Warning:  require(/var/www/kstu/bootstrap/../vendor/autoload.php): failed to open stream: No such file or directory in /var/www/kstu/bootstrap/autoload.php on line 17
PHP Fatal error:  require(): Failed opening required '/var/www/kstu/bootstrap/../vendor/autoload.php' (include_path='.:/usr/share/php') in /var/www/kstu/bootstrap/autoload.php on line 17

Saya sudah mencoba memperbarui Komposer tetapi dikatakan:

heartprogrammer@heartprogrammer-desktop:/var/www/kstu$ composer update
Loading composer repositories with package information
Updating dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - phpunit/phpunit 4.8.9 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.8 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.7 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.6 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.5 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.4 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.3 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.26 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.25 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.24 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.23 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.22 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.21 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.20 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.2 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.19 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.18 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.17 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.16 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.15 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.14 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.13 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.12 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.11 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.10 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.1 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.8.0 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.7.7 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.7.6 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.7.5 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.7.4 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.7.3 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.7.2 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.7.1 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.7.0 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.6.9 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.6.8 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.6.7 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.6.6 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.6.5 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.6.4 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.6.3 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.6.2 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.6.10 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.6.1 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.6.0 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.5.1 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.5.0 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.4.5 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.4.4 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.4.3 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.4.2 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.4.1 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.4.0 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.3.5 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.3.4 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.3.3 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.3.2 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.3.1 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.3.0 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.2.6 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.2.5 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.2.4 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.2.3 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.2.2 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.2.1 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.2.0 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.1.6 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.1.5 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.1.4 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.1.3 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.1.2 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.1.1 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.1.0 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.9 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.8 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.7 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.6 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.5 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.4 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.3 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.20 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.2 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.19 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.18 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.17 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.16 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.15 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.14 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.13 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.12 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.11 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.10 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.1 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 4.0.0 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - Installation request for phpunit/phpunit ~4.0 -> satisfiable by phpunit/phpunit[4.0.0, 4.0.1, 4.0.10, 4.0.11, 4.0.12, 4.0.13, 4.0.14, 4.0.15, 4.0.16, 4.0.17, 4.0.18, 4.0.19, 4.0.2, 4.0.20, 4.0.3, 4.0.4, 4.0.5, 4.0.6, 4.0.7, 4.0.8, 4.0.9, 4.1.0, 4.1.1, 4.1.2, 4.1.3, 4.1.4, 4.1.5, 4.1.6, 4.2.0, 4.2.1, 4.2.2, 4.2.3, 4.2.4, 4.2.5, 4.2.6, 4.3.0, 4.3.1, 4.3.2, 4.3.3, 4.3.4, 4.3.5, 4.4.0, 4.4.1, 4.4.2, 4.4.3, 4.4.4, 4.4.5, 4.5.0, 4.5.1, 4.6.0, 4.6.1, 4.6.10, 4.6.2, 4.6.3, 4.6.4, 4.6.5, 4.6.6, 4.6.7, 4.6.8, 4.6.9, 4.7.0, 4.7.1, 4.7.2, 4.7.3, 4.7.4, 4.7.5, 4.7.6, 4.7.7, 4.8.0, 4.8.1, 4.8.10, 4.8.11, 4.8.12, 4.8.13, 4.8.14, 4.8.15, 4.8.16, 4.8.17, 4.8.18, 4.8.19, 4.8.2, 4.8.20, 4.8.21, 4.8.22, 4.8.23, 4.8.24, 4.8.25, 4.8.26, 4.8.3, 4.8.4, 4.8.5, 4.8.6, 4.8.7, 4.8.8, 4.8.9].

  To enable extensions, verify that they are enabled in those .ini files:
    - /etc/php/5.6/cli/php.ini
    - /etc/php/5.6/cli/conf.d/10-opcache.ini
    - /etc/php/5.6/cli/conf.d/10-pdo.ini
    - /etc/php/5.6/cli/conf.d/20-calendar.ini
    - /etc/php/5.6/cli/conf.d/20-ctype.ini
    - /etc/php/5.6/cli/conf.d/20-exif.ini
    - /etc/php/5.6/cli/conf.d/20-fileinfo.ini
    - /etc/php/5.6/cli/conf.d/20-ftp.ini
    - /etc/php/5.6/cli/conf.d/20-gettext.ini
    - /etc/php/5.6/cli/conf.d/20-iconv.ini
    - /etc/php/5.6/cli/conf.d/20-json.ini
    - /etc/php/5.6/cli/conf.d/20-mbstring.ini
    - /etc/php/5.6/cli/conf.d/20-mcrypt.ini
    - /etc/php/5.6/cli/conf.d/20-phar.ini
    - /etc/php/5.6/cli/conf.d/20-posix.ini
    - /etc/php/5.6/cli/conf.d/20-readline.ini
    - /etc/php/5.6/cli/conf.d/20-shmop.ini
    - /etc/php/5.6/cli/conf.d/20-sockets.ini
    - /etc/php/5.6/cli/conf.d/20-sysvmsg.ini
    - /etc/php/5.6/cli/conf.d/20-sysvsem.ini
    - /etc/php/5.6/cli/conf.d/20-sysvshm.ini
    - /etc/php/5.6/cli/conf.d/20-tokenizer.ini
  You can also run `php --ini` inside terminal to see which files are used by PHP in CLI mode.
heartprogrammer@heartprogrammer-desktop:/var/www/kstu$

Ekstensi diaktifkan dari /etc/php/5.6/apache2/php.ini.

extension=php_bz2.dll
extension=php_curl.dll
extension=php_fileinfo.dll
extension=php_gd2.dll
extension=php_gettext.dll
extension=php_gmp.dll
extension=php_intl.dll
extension=php_imap.dll
extension=php_interbase.dll
extension=php_ldap.dll
extension=php_mbstring.dll
extension=php_exif.dll      ; Must be after mbstring as it depends on it
extension=php_mysql.dll
extension=php_mysqli.dll
extension=php_oci8_12c.dll  ; Use with Oracle Database 12c Instant Client
extension=php_openssl.dll
extension=php_pdo_firebird.dll
extension=php_pdo_mysql.dll
extension=php_pdo_oci.dll
extension=php_pdo_odbc.dll
extension=php_pdo_pgsql.dll
extension=php_pdo_sqlite.dll
extension=php_pgsql.dll
extension=php_shmop.dll

; The MIBS data available in the PHP distribution must be installed.
; See http://www.php.net/manual/en/snmp.installation.php
extension=php_snmp.dll

extension=php_soap.dll
extension=php_sockets.dll
extension=php_sqlite3.dll
extension=php_sybase_ct.dll
extension=php_tidy.dll
extension=php_xmlrpc.dll
extension=php_xsl.dll

Apa yang saya lakukan salah?

Anda perlu menginstal ekstensi dom php.

sudo apt-get install php-xml

Tetapi karena Anda masih menggunakan php5.6 ...

sudo apt-get install php5.6-xml

..akan lakukan triknya.

Seseorang dapat menginstal paket-paket yang diperlukan 1 per 1. Tapi untuk memudahkannya, cobalah

sudo apt-get install php5.6-*

ini akan menginstal semua yang terkait dengan php5.6

Anda perlu menginstal php5.6-xml sudo apt-get install -y php5.6-xmldan composer update. Kemungkinan besar Anda juga kehilangan mbstring. Jika Anda mendapatkan kesalahan, instal paket ini juga dengan:sudo apt-get install php-mbstring