Before to open a ticket, because maybe the problem is mine...
[ SS4 beta 1, wamp server (local), php 7 ]
The instalation crash with
Setting up 'mysite/_config.php'...
Setting up C:\wamp64\www\Silverstripe4/mysite/_config.php
Setting up 'mysite/_config/config.yml'
Setting up C:\wamp64\www\Silverstripe4/mysite/_config/config.yml
Setting up '.htaccess' file...
Setting up C:\wamp64\www\Silverstripe4/.htaccess
Building database schema...
[Warning] Creating default object from empty value
POST /Silverstripe4/install.php
Line 233 in C:\wamp64\www\Silverstripe4\framework\src\Dev\Install\Installer.php
Source
224 $dbAdmin = new DatabaseAdmin();
225 $dbAdmin->setRequest($request);
226 $dbAdmin->pushCurrent();
227 $dbAdmin->doInit();
228 $dbAdmin->doBuild(true);
229
230 // Create default administrator user and group in database
231 // (not using Security::setDefaultAdmin())
232 $adminMember = DefaultAdminService::singleton()->findOrCreateDefaultAdmin();
233 $adminMember->Email = $config['admin']['username'];
234 $adminMember->Password = $config['admin']['password'];
235 $adminMember->PasswordEncryption = Security::config()->get('encryption_algorithm');
236
237 try {
238 $this->statusMessage('Creating default CMS admin account...');
239 $adminMember->write();
Trace
Monolog\ErrorHandler->handleError(2,Creating default object from empty value,C:\wamp64\www\Silverstripe4\framework\src\Dev\Install\Installer.php,233,Array)
Installer.php:233
SilverStripe\Dev\Install\Installer->SilverStripe\Dev\Install\{closure}(SilverStripe\Control\HTTPRequest)
call_user_func(Closure,SilverStripe\Control\HTTPRequest)
HTTPApplication.php:66
SilverStripe\Control\HTTPApplication->SilverStripe\Control\{closure}(SilverStripe\Control\HTTPRequest)
HTTPMiddlewareAware.php:65
SilverStripe\Control\HTTPApplication->callMiddleware(SilverStripe\Control\HTTPRequest,Closure)
HTTPApplication.php:67
SilverStripe\Control\HTTPApplication->execute(SilverStripe\Control\HTTPRequest,Closure,1)
Installer.php:249
SilverStripe\Dev\Install\Installer->install(Array)
install5.php:270
include(C:\wamp64\www\Silverstripe4\framework\src\Dev\Install\install5.php)
install.php:27
include(C:\wamp64\www\Silverstripe4\framework\src\Dev\Install\install.php)
install.php:15