Sometimes running xdebug with PHPStorm will not kill a php built-in web server after it's done, resulting in an error saying that something is already listening on that port.

Find a rogue built-in php server that's listening on a port, and kill it

Find what's listening on port 8080
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sudo lsof -P -iTCP -sTCP:LISTEN | grep -i 8080

ex. output
----------
php       8046 username    5u  IPv4 0xd9c3cdd5c98d4b65      0t0  TCP localhost:8080 (LISTEN)

Kill It
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kill 8046