I found three code formatters for PHP.
Prettier (With PHP Plugin)
PrettyPHP (https://github.com/lkrms/vscode-pretty-php)
phpfmt (https://github.com/kokororin/vscode-phpfmt)
I was able to setup Prettier with the PHP plugin but the setup is not ideal since I have to install prettier and the prettier PHP plugin from NPM into the project every single time which is not the case when using Prettier VSCode extension with HTML, JS and CSS. I do like how Prettier has its own configuration .prettierrc files and it allows you to set a standard format for a project you are collaborating with others, however I believe formatting should be done in the IDE such as using a VSCode extension and this is the case with the Prettier extension for HTML, JS and CSS but not for PHP since it requires NPM packages.
The other two do not look popular. Am I missing something? I would like to have a standard format or be able to have an opinionated format setup like Prettier for JS but for PHP.
Videos
Update 2021-07-21
It's been more than half a decade since I first wrote this answer. The extensions to which I originally linked are abandoned, and Visual Studio Code's intrinsic PHP support hasn't improved, which is disappointing. The only decent extension still standing of which I'm aware is PHP Intelephense, which uses a freemium model: basic features are free, and a lifetime license is $12 USD as of writing.
The free version of Intelephense supports code formatting with the usual shortcuts (Alt + Shift + F on Windows and Linux, ⌥⇧F on macOS). Visual Studio Code continues to lack built-in support for PHP code formatting and will direct you to the extension marketplace if you attempt to format PHP without an appropriate extension installed.
Original answer
Visual Studio Code has pretty awesome PHP support. What it lacks is covered by extensions. A quick search reveals at least three (1, 2, and 3) that claim to support PHP formatting.
They mostly seem to use the standard shortcut of Alt + Shift + F on Windows/Linux, with varying shortcuts on Mac. If you're on Mac, give ⌥⇧F a try.
I installed
Prettier for HTML, CSS, and JavaScript files
PHP Intelephense for PHP files
I followed the instructions for each plugin but found I had to additionally edit settings.json manually in order to get them to work together.
"editor.defaultFormatter": "esbenp.prettier-vscode",
"[php]": {
"editor.defaultFormatter": "bmewburn.vscode-intelephense-client"
}
The settings use Intelephense as the formatter for PHP files and use Prettier as the formatter for all other files.
Now I use Shift + Alt + F to format the files like everybody else.