You can do it with a macro extension like multi-command. You do have to hard-code a rough guess as to how far to the right you want to align the comments. You can't simply measure the furthest and use that - you would need a more involved extension to do that. However, you will have multi-cursors at the end and it is easy to adjust all the comments at once if you don't like where they ended up as in the demo where backspacing and tabbing moves all the comments in alignment.
Demo:

Use some keybinding to trigger the macro:
{
"key": "alt+w", // whatever keybinding you choose
"command": "extension.multiCommand.execute",
"args": { "command": "multiCommand.alignComments" },
"when": "editorTextFocus && !editorReadonly && resourceExtname =~ /\\.js/"
},
I made that for .js files but you can modify that for other extensions, like
resourceExtname =~ /\\.(js$|php)/ for .js and .php files.
And in your settings.json the actual macro:
"multiCommand.commands": [
{
"command": "multiCommand.alignComments",
// "interval": 3000,
"sequence": [
"editor.action.insertCursorAtEndOfEachLineSelected",
"cursorHomeSelect",
{
"command": "editor.action.insertSnippet", // pad with lots of spaces's'
"args": {
// so capture group 1 is before the comment, add spaces after it
"snippet": "${TM_SELECTED_TEXT/^([^;]+;)(\\s*)(?=\\/\\/.*)/$1 /g}",
}
},
"cursorHomeSelect",
{
"command": "editor.action.insertSnippet",
"args": {
// keep first 25 characters or wherever you want to align
// and then add the comments
"snippet": "${TM_SELECTED_TEXT/(.{25})(\\s*)(.*)/$1$3/g}",
}
},
// "removeSecondaryCursors" // to exit multi-cursor mode
]
}
]
Just hit Escape to exit multi-cursor mode (or add that command to the end of the macro).