php
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1<?php
2
3// Function to get a number's square
4function square($n) {
5    return $n * $n;
6}
7
8$numbers = [1, 2, 3, 4, 5];  // our data stream
9
10// array_map applies the square function to each number in the array
11$squared_numbers = array_map('square', $numbers);
12
13// Print squared numbers
14foreach ($squared_numbers as $n) {
15    echo $n . " ";
16}
17// Output: 1 4 9 16 25
18
19?>

php
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1<?php
2
3// Array of uppercase sentences
4$sentences = ["HELLO WORLD", "PHP IS FUN", "I LIKE PROGRAMMING"];  // our data stream
5
6// array_map applies an anonymous function to each sentence in the array
7$lower_sentences = array_map(function($s) {
8    return strtolower($s);
9}, $sentences);
10
11// Print lowercased sentences
12foreach ($lower_sentences as $sentence) {
13    echo $sentence . "\n";
14}
15// Output: hello world
16//         php is fun
17//         i like programming
18
19?>

php
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1<?php
2
3// Array of sentences
4$sentences = ["HELLO WORLD", "PHP IS FUN", "I LIKE PROGRAMMING"];  // our data stream
5
6// Filtering sentences that contain 'PHP'
7$filtered_sentences = array_filter($sentences, function($s) {
8    return strpos($s, 'PHP') !== false;
9});
10
11// Converting filtered sentences to lowercase
12$lower_filtered_sentences = array_map(function($s) {
13    return strtolower($s);
14}, $filtered_sentences);
15
16// Print filtered and lowercased sentences
17foreach ($lower_filtered_sentences as $sentence) {
18    echo $sentence . "\n";
19}
20// Output: php is fun
21
22?>

php
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1<?php
2
3class DataProjector {
4    private $data;
5
6    public function __construct($data) {
7        $this->data = $data;
8    }
9
10    // Method to apply a function to each element
11    public function project($func) {
12        return array_map($func, $this->data);
13    }
14
15    // Method to filter data and apply a function to each filtered element
16    public function filter_and_project($filter_func, $project_func) {
17        $filtered_data = array_filter($this->data, $filter_func);
18        return $this->project($project_func, $filtered_data);
19    }
20}
21
22// Function to check if a string contains "PHP"
23function contains_php($s) {
24    return strpos($s, 'PHP') !== false;
25}
26
27// Function to convert a string to lowercase
28function to_lowercase($s) {
29    return strtolower($s);
30}
31
32$sentences = ["HELLO WORLD", "PHP IS FUN", "I LIKE PROGRAMMING"];  // our data stream
33
34// Creating a DataProjector object with our sentences
35$projector = new DataProjector($sentences);
36
37// Applying filter_and_project to filter sentences containing 'PHP' and convert them to lowercase
38$lower_filtered_sentences = $projector->filter_and_project('contains_php', 'to_lowercase');
39
40// Print filtered and lowercased sentences
41foreach ($lower_filtered_sentences as $sentence) {
42    echo $sentence . "\n";
43}
44// Output:
45// php is fun
46
47?>