There is no “global” setting for existing projects — it needs to be done for each project individually (Spell Checker is an inspection and Inspections are configured on per-project level).
You need to disable whole group at Settings/Preferences | Editor | Inspections | Proofreading (used to be Spelling before).
You can configure it to be disabled by default for any future new projects at File | New Projects Setup | Settings for New Projects... (previously was File | Default Settings).
https://www.jetbrains.com/help/phpstorm/2021.2/configure-project-settings.html#new-default-settings
Also check suggestion by @Amged — edit your Color Schema to simply remove any visual effects for misspelt words: Settings/Preferences | Editor | Colors & Fonts | General --> Errors & Warnings | Typo.
This way it will affect ALL projects straight away as long you use that Color Schema. It will also allow you to still list all typos if you run Code | Inspect Code....
The possible down-side: spell checker still runs; you will see extra 2 menu entries when right clicking on such words.
