Setting PHP validation to false in Preferences/User settings.json and/or Preferences/Workspace settings.json does currently work in Windows (year 2016, VSC Version 1.4.0) to end the validation messages. User preference settings are applied globally, while Workspace settings are applied to specific folders or projects.
Just to clarify what may not be obvious to newbies, custom settings in User 'settings.json' and Workspace 'settings.json' pages must be bracketed, otherwise the defaults will not be overwritten.
After the settings have been entered, the page must be saved (File/Save). A backup of 'settings.json' may be exported via Save As by changing the file name and/or choosing another folder. For example, 'myfolder\2017-01-01_vsc_user_settings.json'. To use the backup file, open it in VSC and copy/paste the code back into Preferences/User or Preferences/Workplace 'settings.json'.
https://code.visualstudio.com/docs/customization/userandworkspace
Turn off PHP validation: settings.json
// Place your settings in this file to overwrite default and user settings.
{
"php.validate.enable": false
}
Use comma separators to overwrite multiple default settings: settings.json.
// Place your settings in this file to overwrite default and user settings.
{
"php.validate.enable": false,
"files.trimTrailingWhitespace": true,
"editor.autoClosingBrackets": false,
"editor.wordWrap": true
}