Functions

What is a Function

• Block of code
• Performs a specific task
• Used throughout your program

<?php
function createName($parameter, $anotherParameter)
{
 //… perform some function here
}
?>

Creating/Calling a function

<?php
listOfBooks();

function listOfBooks()
{
    echo "Hamlet<br>";
    echo "Romeo and Juliet<br>";
}
//output: Hamlet
//Romeo and Juliet
?>

<?php
function bookByAuthorYear($authorName, $year)
{
    echo $year;
    echo "\n";
    echo $authorName;
}
$authorName = "William Shakespeare";
bookByAuthorYear($authorName, 1910);
?>

Passing/Default parameters

<?php
function bookByAuthorYear($tempAuthorName, $tempYear = 1910)
{
    echo $tempYear;
    echo "<br>";
    echo $tempAuthorName;
    echo "<br>";
}
$year = 1920;
$authorName = "William Shakespeare";
bookByAuthorYear($authorName);
bookByAuthorYear($authorName, $year);
//output:
//1910
//William Shakespeare
//1920
//William Shakespeare
?>

Note

All required parameters shoud be at the begining of the function parameter and defaults should be at the end.

Returning Values

<?php
function bookByAuthorYear($authorName)
{
    echo $authorName;
}
function getAuthor()
{
    return "William Shakespeare";
}
bookByAuthorYear(getAuthor());
//output: William Shakespeare
?>

Variable Functions

<?php
function getAuthor()
{
    echo "Charles Dickens";
}
$variableFunctionName = "getAuthor";
$variableFunctionName();
//output: Charles Dickens
?>

Variable Scope

<?php
$authorName = "William Shakespeare";
function setAuthorName()
{
    $authorName = "Charles Dickens";
    echo $authorName;
}
setAuthorName();
echo "<br>";
echo $authorName;
//output:
//Charles Dickens
//William Shakespeare
?>

Function Global Scope

<?php
$authorName = "William Shakespeare";
function setAuthorName()
{
    Global $authorName;
    $authorName = "Charles Dickens";
}
setAuthorName();
echo $authorName;
//output: Charles Dickens
?>