In this activity you will learn some advanced array techniques for arrays in PHP, which will be useful when processing data from a database.

• Create a new file called 'arrays.php' in your top level directory using Visual Studio Code.
• Prepare it with the usual code for a basic file.

<?php
    include('header.php');
    include('menu.php');
?>
    <main>
    </main>
<?php
    include('footer.php');
?>

• We've seen how to create an array like this.

$animals = array('dog', 'elephant', 'rabbit');

• This allows us to access each item in the array by number ($animals[0]).
• For greater flexibility, in PHP (unlike in Javascript) we can assign names for each element.
• Add the following code inside the first PHP block of 'arrays.php'.

    $animals = array('item1' => 'dog', 'item2' => 'elephant', 'item3' => 'rabbit');

• Now, let's display this inside the <main> tag.

    echo $animals;

• This won't work. When you view the page, you'll see the word 'Array' only. echo doesn't work for arrays.
• Try this instead.

    print_r($animals);

• print_r is a
• When you view the page, you'll see some complicated text that looks something like the array.
• To see it properly, right click on the page and select 'View Page Source'.
• Now the formatting is much better and you can clearly read the array.
• This is one way to create such an array, We can also assign each item separately.

    $animals['item1'] = 'dog';
    $animals['item2'] = 'elephant';
    $animals['item3'] = 'rabbit';

• We can read the array in the same way. Add this code to the <main> tag.

    echo "MURRAY: the first item of animals is $animals['item1'].";

• Now view the page and check the results.

• We've seen how to do a 'for loop' in an earlier class, but there's another loop that is extremely useful for processing arrays. It's the 'foreach' loop.
• Add the following PHP code to the <main> tag after creating your array.

    foreach($animals as $name => $item) {
        echo "MURRAY: $name is a $item";
    }

• The first line sets up the loop. It says 'run through this code for each item in the array $animals, where the reference for each item is $name and the item itself is $item'.
• We can now refer to the name and the actual item by using the variables $name and $item.
• echo then display these values so that we can read them in the HTML code.
• Try it now to be sure you understand it.

• Just as in Javascript, PHP has many types of loops. The next we'll look at is the 'while loop'.
• Add the following code inside a PHP block. It might be best to put it at the end to keep it separate. Change my name to yours so you can find your results in the logs.

    $i = 0;
    while ($i < 10) {
        error_log("MURRAY: the value of i is $i");
        $i++;
    }

• $i = 0; defines a variable and sets it to '0'.
• while ($i < 10) {} runs the code inside {} as long as $i is less than 10.
• error_log("MURRAY: the value of i is $i"); outputs a string containing the value of $i to the logs so we can see it.
• Finally, $i++; increments $i each loop so that it doesn't go on forever.
• Open the page 'mysql.php' and check your logs using Putty.

cat /var/log/apache2/error.log | grep 'MURRAY'

• You should see your text ten times with the number increasing from 0 to 9.
• So this is another way of running the same code multiple times.

• Objects are an advanced data structure and we won't go into it too much here, but you'll need to understand a little bit to use the PHP database connection.
• An object is like a named array where you can access each element by name.
• But an object also has functions built into. Recall that in Javascript audio has built-in functions like .play(), .paused() and built-in information like .paused. That's because audio is an object.
• Similarly, in PHP, an object can have both data and functions. For example, a database connection object can have information about the connection and also have functions to extract data.
• Whereas you access the information in an array using [] , we access information and functions using ->.
• To use an abstract example, we could create an object called $table.
• We could set the number of legs on the table as follows.

$table->legs = 4;

• We could also move the table to another location as follows.

$table->move($location);

• There is a whole school of programming based on objects (Object-oriented programming) and objects could be the subject of many classes, but this is all you need to know to use the database connection.

Next: Tables