How to Disable Spell Checking for All My Projects

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).

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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

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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.

You could leave the Spell Checking inspection enabled and just remove the visual effect in the editor by going to Settings | Colors & Fonts | General | Typo and unchecking Effect. This way it will not highlight the typos in the editor but when you manually run the code inspector the typos are listed.

I'm working with "CLion" but I'm pretty sure the settings are pretty much close to "phpstorm" as both of them are produced by the same company :)

Go to the File tab and then select settings. In the opened window select the items as the picture below and uncheck the spelling item.