call function in constructor wordpress add_action code example

Example 1: how to define function in php

<?php
function writeMsg() {
    echo "Hello world!";
}

writeMsg(); //call the function
?>

Example 2: how to call a static method in java

class scratch{
	public static hey(){
		System.out.println("Hey");
    }
	public static void main(String[] args){
		hey();
        //print Hey to the console
    }