Nginx调用PHP-FPM出现「Primary script unknown」错误的排查求助

各位大佬好，我最近在配置Nginx+PHP-FPM的时候碰到了一个棘手的问题——请求/api/user.php时总是返回404，同时Nginx错误日志里一直报「Primary script unknown」，折腾了好一阵没找到根源，想请大家帮忙排查一下问题所在！

Nginx错误日志（error.log）内容： #

[error] 10910#10910: *7 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: 127.0.0.1, server: localhost, request: "GET /api/user.php HTTP/2.0", upstream: "fastcgi://unix:/run/php/php8.1-fpm.sock:", host: "localhost"

Nginx访问日志（access.log）内容： #

127.0.0.1 - - [10/Jun/2023:15:57:33 +0200] "GET /api/user.php HTTP/2.0" 404 16 "-" "curl/7.88.1"

我的Nginx配置文件内容： #

pid /path/to/my/directory/nginx.pid;

user seba www-data;

include /etc/nginx/modules-enabled/*.conf;

events {
    worker_connections 1024;
}

http {
    # HTTP server
    server {
        listen 8080;
        server_name syskeep;

        # Redirect all HTTP traffic to HTTPS
        return 301 https://$host$request_uri;
    }

    # HTTPS server
    server {
        listen 443 ssl http2;
        # Uncomment to let SysKeep public available
        # listen [::]:443 ssl http2;

        server_name localhost;

        root /path/to/my/directory/public/;
        index index.html index.php;

        try_files $uri $uri/ =404;

        # SSL certificate files
        ssl_certificate /path/to/my/directory/localhost.pem;
        ssl_certificate_key /path/to/my/directory/localhost-key.pem;

        # SSL configuration
        ssl_protocols TLSv1.2 TLSv1.3;
        ssl_prefer_server_ciphers on;
        ssl_ciphers 'EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH';

        # Add security-related headers
        add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always;
        add_header X-Content-Type-Options nosniff;
        add_header X-Frame-Options "SAMEORIGIN";
        add_header X-XSS-Protection "1; mode=block";
        add_header Referrer-Policy "strict-origin-when-cross-origin";

        location ^~ /api {
            alias /path/to/my/directory/core/src/public/;
            try_files $uri =404;
            fastcgi_intercept_errors on;
            fastcgi_pass unix:/run/php/php8.1-fpm.sock;
            fastcgi_index index.php;
            fastcgi_param SCRIPT_FILENAME $document_root/$fastcgi_script_name;
            include /etc/nginx/fastcgi_params;
        }
    }

    types {
        application/javascript js;
        text/css css;
        text/html html;
    }
}

测试结果： #

我用curl测试接口时，执行命令：

curl https://localhost/api/user.php

得到的响应体是：

File not found.

同时返回的HTTP状态码是404。

另外补充一下，我启动Nginx使用的是自定义配置文件，命令是：

nginx -c /path/to/custom/nginx.conf

麻烦各位帮忙看看哪里出问题了，谢谢！

备注：内容来源于stack exchange，提问作者user18545619