typing localhost in browser which send me to main page of my php project

typing localhost in browser which send me to main page of my php project

i have a php project which has many php files. i have configured it
properly. and its working. but i want that whenever i type localhost in my
browser, it should lead to the main page of my php project. Right now, the
scenario is whenever i write localhost on my brower, it shows the php
directory like this-
Index of /
adddet.php
client/
dbconn.php
deldet.php
login.php
main.php
i want to show main.php whenever i write localhost on browser address bar.