Welcome to today's lesson! Our topic for the day is data aggregation, a crucial aspect of data analysis. Like summarizing a massive book into key points, data aggregation summarizes large amounts of data into important highlights.

By the end of today, you'll be equipped with several aggregation methods to summarize data streams in PHP. Let's get started!

Let's say we have an array of integers denoting the ages of a group of people. We will demonstrate several basic aggregation methods using PHP's built-in functions:

php
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1<?php
2
3$ages = [21, 23, 20, 25, 22, 27, 24, 22, 25, 22, 23, 22];
4
5// Number of people
6$num_people = count($ages);
7echo "Number of people: $num_people\n";
8
9// Total age
10$total_ages = array_sum($ages);
11echo "Total age: $total_ages\n";
12
13// Youngest age
14$youngest_age = min($ages);
15echo "Youngest age: $youngest_age\n";
16
17// Oldest age
18$oldest_age = max($ages);
19echo "Oldest age: $oldest_age\n";
20
21// Average age
22$average_age = $total_ages / $num_people;
23echo "Average age: $average_age\n";
24
25// Age range
26$age_range = $oldest_age - $youngest_age;
27echo "Age range: $age_range\n";
28
29?>

Here's a brief overview of the above code snippet:

1. Number of people: Uses count() to get the number of elements in the array.
2. Total age: Uses array_sum() to sum all elements in the array.
3. Youngest age: Uses min() to find the smallest element.
4. Oldest age: Uses max() to find the largest element.
5. Average age: Calculates the average age by dividing the total age by the number of people.
6. Age range: Computes the range of ages by subtracting the youngest age from the oldest age.

These functions provide essential aggregation operations and are widely used with data streams.

For deeper analysis, such as calculating the mode, or most frequent age, we can use PHP's foreach loops.

For example, using foreach loops, we can find the mode or most frequent age:

php
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1<?php
2
3$ages = [21, 23, 20, 25, 22, 27, 24, 22, 25, 22, 23, 22];
4
5// Initialize an associative array to store the frequency of each age
6$frequencies = [];
7
8// Use a foreach loop to populate frequencies
9foreach ($ages as $age) {
10    if (!isset($frequencies[$age])) {
11        $frequencies[$age] = 0;
12    }
13    $frequencies[$age]++;
14}
15
16// Find the age with max frequency
17$max_freq = 0;
18$mode_age = -1;
19foreach ($frequencies as $age => $freq) {
20    if ($freq > $max_freq) {
21        $max_freq = $freq;
22        $mode_age = $age;
23    }
24}
25echo "Max frequency: $max_freq\n"; // Max frequency: 4
26echo "Mode age: $mode_age\n"; // Mode age: 22
27
28?>

Fantastic! You've just learned how to use basic and advanced data aggregation methods in PHP. These techniques are pivotal in data analysis and understanding. Now, get ready for the practical tasks lined up next. They'll reinforce the skills you've just gained. Remember, the more you practice, the better you become. Good luck with your practice!