My phpmyadmin is working normally, but why does the error prompt appear when I use mysql_connent ()?

My phpmyadmin works normally, but why is an error prompted when I use mysql_connent? I have configured php and mysql, and can access and modify the database normally from phpmyadmin. but somehow, I access the database from my own function, "undefined function" is always prompted. my phpmyadmin is working normally. but why is an error prompted when I use mysql_connent?
I have configured php and mysql, and can access and modify the database normally from phpmyadmin. but somehow, when I access the database from my own function, the system will always prompt "undefined function"

 
$ Host = "localhost ";

$ Username = "root ";

$ Passowrd = "123456 ";

$ Dbname = "test ";

$ Res = mysql_connent ($ host, $ username, $ password) or die (mysql_error ());

@ Mysql_select_db ($ dbname );

?>

How can this be solved?
------ Best solution --------------------
Mysql_connent-> mysql_connect