Hi @Christopher ,
Apologies for this being an answer rather than a comment. I deployed QuickStart | Create a PHP web app in Azure App Service to a PHP 8 instance and didn't run into any issues.
2021-09-10T23:11:38.535548257Z Cannot load Zend OPcache - it was already loaded
2021-09-10T23:11:39.789941059Z _____
2021-09-10T23:11:39.789986759Z / _ \ __________ _________ ____
2021-09-10T23:11:39.789994159Z / /_\ \___ / | \_ __ \_/ __ \
2021-09-10T23:11:39.789998059Z / | \/ /| | /| | \/\ ___/
2021-09-10T23:11:39.790001859Z \____|__ /_____ \____/ |__| \___ >
2021-09-10T23:11:39.790005659Z \/ \/ \/
2021-09-10T23:11:39.790009259Z A P P S E R V I C E O N L I N U X
2021-09-10T23:11:39.790012759Z
2021-09-10T23:11:39.790015959Z Documentation: http://aka.ms/webapp-linux
2021-09-10T23:11:39.790019159Z PHP quickstart: https://aka.ms/php-qs
2021-09-10T23:11:39.790022459Z PHP version : 8.0.3
2021-09-10T23:11:39.790025559Z Note: Any data outside '/home' is not persisted
2021-09-10T23:11:40.543063020Z Running oryx create-script -appPath /home/site/wwwroot -output /opt/startup/startup.sh -bindPort 8080 -startupCommand 'php-fpm;'
2021-09-10T23:11:41.094042003Z Cound not find build manifest file at '/home/site/wwwroot/oryx-manifest.toml'
2021-09-10T23:11:41.094068403Z Could not find operation ID in manifest. Generating an operation id...
2021-09-10T23:11:41.094074203Z Build Operation ID: 24f0d2ac-3d6f-4dca-a06d-aac62a0ffb82
2021-09-10T23:11:42.197972581Z Writing output script to '/opt/startup/startup.sh'
2021-09-10T23:11:44.013553473Z Starting nginx: nginx.
2021-09-10T23:11:44.622710340Z Cannot load Zend OPcache - it was already loaded
2021-09-10T23:11:44.813785586Z [10-Sep-2021 23:11:44] NOTICE: fpm is running, pid 41
2021-09-10T23:11:44.823348893Z [10-Sep-2021 23:11:44] NOTICE: ready to handle connections
2021-09-10T23:11:44.862389123Z 127.0.0.1 - 10/Sep/2021:23:11:44 +0000 "GET /index.php" 200
2021-09-10T23:11:44.899374751Z 127.0.0.1 - 10/Sep/2021:23:11:44 +0000 "GET /index.php" 200
2021-09-10T23:11:44.907903958Z 127.0.0.1 - 10/Sep/2021:23:11:44 +0000 "GET /index.php" 200
2021-09-10T23:11:50.191704685Z 127.0.0.1 - 10/Sep/2021:23:11:50 +0000 "GET /index.php" 200
2021-09-10T23:11:55.415926414Z 127.0.0.1 - 10/Sep/2021:23:11:55 +0000 "GET /index.php" 200
2021-09-10T23:11:56.439731573Z 127.0.0.1 - 10/Sep/2021:23:11:56 +0000 "GET /index.php" 200
2021-09-10T23:12:00.644475051Z 127.0.0.1 - 10/Sep/2021:23:12:00 +0000 "GET /index.php" 200
2021-09-10T23:12:05.920874158Z 127.0.0.1 - 10/Sep/2021:23:12:05 +0000 "GET /index.php" 200
2021-09-10T23:12:11.149657153Z 127.0.0.1 - 10/Sep/2021:23:12:11 +0000 "GET /index.php" 200
2021-09-10T23:12:16.468328599Z 127.0.0.1 - 10/Sep/2021:23:12:16 +0000 "GET /index.php" 200
However, I am noticing that a composer.phar was found and oryx is attempting to pull those dependencies. Can you provide your composer.phar so that I can try to repro your issue?