Introduction to Functions in PHP

return statement in PHP

The return statement is used to return the final output of a function. Once the first return statement is executed, the function is exited.

function returnMe(){
  return 6;
  //this value is returned
  return 8;
  //this statement is not executed
}

echo returnMe();

Invoking a function in PHP

Functions are invoked by using the function name followed by parentheses.

//First the function needs to be defined:
function callFunc() {
  //code goes here
}

//Then the function can be invoked:
callFunc();

Define PHP Function

A function contains a set of instructions to be executed. It is defined by using the keyword function followed by the name of the function, the parentheses which contain the parameters, and finally the curly braces which contain the code block.

function plus($x,$y){
    return $x + $y;
}

echo plus(10, 5); 
//prints "15"

Camel Case Function

When writing a function in PHP, the convention is to use camel case. This means that we start with a lowercase letter and then capitalize the first letter of every new word.

Additionally, the function name should typically start with a verb.

// This is a camel case function 
function calculateSum() {}

// This is not a camel case function; it is a snake_case function 
function calculate_sum() {}

// This is not a camel case function 
function CalculateSum() {}

PHP Variable Scope

A variable with local scope can only be accessed within the function it is declared. A variable with global scope can be accessed from multiple functions in the PHP script.

<?php

$x = 6;

function scope(){
    $y = 7;

    echo $x;
    // prints 'undefined variable'
  
    global $x;
    echo $x;
    // prints 6
    
    echo $y;
    // prints 7
}

scope();