Composer will not install, what should I do?

The PHP exe file you specified did not run correctly [exit code -2]: C:\xampp\php\php.exe

Program Output: PHP Warning: PHP Startup: Unable to load dynamic library 'bz2' (tried: C:\xampp4\php\ext\bz2 (The specified module could not be found), C:\xampp4\php\ext\php_bz2.dll (The specified module could not be found)) PHP Warning: PHP Startup: Unable to load dynamic library 'curl' (tried: C:\xampp4\php\ext\curl (The specified module could not be found), C:\xampp4\php\ext\php_curl.dll (The specified module could not be found)) PHP Warning: PHP Startup: Unable to load dynamic library 'fileinfo' (tried: C:\xampp4\php\ext\fileinfo (The specified module could not be found), C:\xampp4\php\ext\php_fileinfo.dll (The specified module could not be found)) PHP Warning: PHP Startup: Unable to load dynamic library 'gettext' (tried: C:\xampp4\php\ext\gettext (The specified module could not be found), C:\xampp4\php\ext\php_gettext.dll (The specified module could not be found)) PHP Warning: PHP Startup: Unable to load dynamic library 'mbstring' (tried: C:\xampp4\php\ext\mbstring (The specified module could not be found), C:\xampp4\php\ext\php_mbstring.dll (The specified module could not be found)) PHP Warning: PHP Startup: Unable to load dynamic library 'exif' (tried: C:\xampp4\php\ext\exif (The specified module could not be found), C:\xampp4\php\ext\php_exif.dll (The specified module could not be found)) PHP Warning: PHP Startup: Unable to load dynamic library 'mysqli' (tried: C:\xampp4\php\ext\mysqli (The specified module could not be found), C:\xampp4\php\ext\php_mysqli.dll (The specified module could not be found)) PHP Warning: PHP Startup: Unable to load dynamic library 'pdo_mysql' (tried: C:\xampp4\php\ext\pdo_mysql (The specified module could not be found), C:\xampp4\php\ext\php_pdo_mysql.dll (The specified module could not be found)) PHP Warning: PHP Startup: Unable to load dynamic library 'pdo_sqlite' (tried: C:\xampp4\php\ext\pdo_sqlite (The specified module could not be found), C:\xampp4\php\ext\php_pdo_sqlite.dll (The specified module could not be found)) PHP Warning: PHP Startup: Unable to load dynamic library 'php_openssl.dll' (tried: C:\xampp4\php\ext\php_openssl.dll (The specified module could not be found), C:\xampp4\php\ext\php_php_openssl.dll.dll (The specified module could not be found)) PHP Warning: PHP Startup: Unable to load dynamic library 'php_ftp.dll' (tried: C:\xampp4\php\ext\php_ftp.dll (The specified module could not be found), C:\xampp4\php\ext\php_php_ftp.dll.dll (The specified module could not be found)) PHP Warning: Cannot open "C:\xampp4\php\extras\browscap.ini" for reading PHP Fatal error: Unable to start standard module