Forem: Yongyao Yan

How to calculate keyword frequency and draw the bar chart in PHP

Yongyao Yan — Mon, 11 Jul 2022 10:09:34 +0000

This post shows you how to calculate the keyword frequency from text and draw the bar chart by using the JpGraph library.

Calculate the keyword frequency

Suppose we have a string like this:

$str = "There are two cats on the table. One on the left side is eating an apple, the other on the right side is eating a fish.";

It is easy to calculate the keyword frequency by using the PHP built-in functions.

First, we convert all text to lowercase.

$str = strtolower($str);

Then, we can extract all words from text by using the function str_word_count().

$words = str_word_count($str, 1);

By setting the second parameter's value to be 1, the function str_word_count() returns an array $words with all the words in the string $str.
After that, use the function array_count_values() to count all the valules inside the array $words.
Actually, it gets the frequency of all the words in the array $words and returns as an array $keywords.

$keywords = array_count_values($words);

If we just want the top 5 keywords, use the function arsort() to sort the array $keywords from highest to lowest and get the first 5 elements by using the function array_splice().

arsort($keywords);
$keywords = array_splice($keywords, 0, 5);

Finally, calculate the percentage of each keyword like this:

$total = count($words);

$frequency = [];
foreach ($keywords as $key => $value) {
    $frequency[$key] = number_format(($value / $total) * 100, 2);
}

Draw the keyword frequency bar chart

In this example, we use the graph creating library, JpGraph, to draw the keyword frequency bar chart.
First, copy the library files under the root path of your website and include the JpGraph files:

require_once ('jpgraph-4.4.1/src/jpgraph.php');
require_once ('jpgraph-4.4.1/src/jpgraph_bar.php');

Then create a graph and set it as autoscaling.

...

For the rest of the content, please go to the link below:
https://www.codebilby.com/blog/a44-calculate-keyword-frequency-and-draw-the-bar-chart-in-php

How to count words in a string in PHP

Yongyao Yan — Wed, 29 Jun 2022 21:04:28 +0000

By using the function str_word_count(), we can get information about words used in a string.

Get the number of words found in a string

To find out how many words in a string, you can do like this:

$str = "aaa bbb ccc 123 ddd";

print_r(str_word_count($str, 0)); // 4

In this example, the function finds 4 words in the string $str and the output is 4. The second parameter in the function str_word_count() specifies the return value of the function. Here, the value 0 specifies returning the number of words in the input string.

Get an array containing all the words found inside the string

If you set the second parameter's value to be 1, the function str_word_count() will return an array with all the words in the string.

$str = "aaa bbb ccc 123 ddd";

print_r(str_word_count($str, 1));

The output is:

Array ( [0] => aaa [1] => bbb [2] => ccc [3] => ddd )

If you want 123 to be considered as a 'word' and extracted from the string, relevant characters need to be specified in the third parameter of the function.

print_r(str_word_count($str, 1, '0..9'));

As shown in the above code snippet, because the number range, i.e. from 0 to 9, is listed in the third parameter, the number 123 is considered as a 'word'. The output is:

Array ( [0] => aaa [1] => bbb [2] => ccc [3] => 123 [4] => ddd )

If you need the numeric position of each word inside the string, you just need to change the third parameter's value to be 2.

$str = "aaa bbb ccc 123 ddd";

print_r(str_word_count($str, 2, '0..9'));

The output is:

Array ( [0] => aaa [4] => bbb [8] => ccc [12] => 123 [16] => ddd )

The key of each array item is the numeric position of the relevant word in the string.

Thanks for reading!
To find more programming tutorials, please visit: CodeBilby.com

Create an object from a string variable in PHP

Yongyao Yan — Sat, 04 Jun 2022 20:09:45 +0000

In PHP, objects can be created from string variables. It provides a very convenient way for you to define rules in text and handle requests dynamically. In this post, we show you how to do it.

Create an object from a string variable

Supposed we have a class called Rectangle, it is for a rectangle shape and it calculates its area.

class Rectangle
{
    private $length;
    private $width;

    public function setLength($l) {
        $this->length = $l;
    }

    public function setWidth($w) {
        $this->width = $w;
    }

    public function setLengthWidth($l, $w) {
         $this->length = $l;
         $this->width = $w;
    }

    public function getArea() {
        return $this->length * $this->width;
    }

}

You can use a string variable to create the Rectangle object like this:

$className = "Rectangle";
$class = new $className();

Also, a function in a class can be called by using a string variable. If you want to call the function setLength() and setWidth() in the class Rectangle, you can do as follows:

$length = 10;
$width = 3;

$setLength = "setLength";
$setWidth = "setWidth";

$class->{$setLength}($length);
$class->{$setWidth}($width);

Or, you can just use a string in the {} to call a function like this:

$class->{"setLengthWidth"}($length, $width);

To calculate the Rectangle's area, the function getArea() can be called as follows:

echo "The area is: " . $class->{"getArea"}(); // The area is: 30

Create rules and call functions dynamically

Here, we show you an example how to call functions dynamically based on the request.
...

For the rest of the content, please go to the link below:
https://www.codebilby.com/blog/a42-create-object-from-variable-name

Reverse an array in PHP by using recursion

Yongyao Yan — Sun, 15 May 2022 13:46:35 +0000

Let's go back to a computer science textbook topic. Show you how to reverse an array in PHP without using any native array functions such as array_xxx().

Recursion

Recursion is a process in computer science to make a function call itself. The corresponding function is called recursive function. Certain complicated problems can be solved easily by using the recursive method.

The best way to understand the recursive function is to show you the example of Fibonacci nunmbers. The Fibonacci numbers can be defined as:

F(0) = 0, F(1) = 1
F(N) = F(N-1) + F(N-2) (N > 1)

The recursive function for the Fibonacci nunmbers is:

function F(int $n): int {
    if ($n == 0) return 0; // Stop condition
    if ($n == 1) return 1; // Stop condition

    return F($n - 1) + F($n - 2);

}

 echo 'F(18) = ' . F(18); // F(18) = 2584

The most important thing in a recursive function is the stop condition, where the function stops calling itself. In the code snippet above, there are two stop conditions:

if ($n == 0) return 0;

and

if ($n == 1) return 1;

These stop conditions are the cases for F(0) = 0 and F(1) = 1. When N > 1, the recursive function calls itself and returns the value of F($n - 1) + F($n - 2). If no stop condition is defined, a recursive function can run into the problem of infinite resursion. This is like the case of infinite looping.

Reversing an array

This is an example of using recursion to reverse an array without using the native array functions, i.e. array_xxx(), in PHP.

We define a recursive function called reverseArray(array $array) to reverse an array. It iterates over an input array and reverses each element's position by calling the function insertToFront() where each element read from the input array is put in the front of the return array $result.

function reverseArray(array $array) {
    $result = [];
    foreach ($array as $key => $value) {
        // check if it is an array
        if (is_array($value)) {
            // insert into the front of the result array
            $result =  insertToFront($key, reverseArray($value), $result);
            continue;
        }      
        $result = insertToFront($key, $value, $result);  
    }
    return $result;

}

In the recursive function reverseArray(array $array), the stop condition is when the element's value type is not an array. Each iterated array element is put to the front of the return array $result in turn:

$result = insertToFront($key, $value, $result);

If the element's value type is an array, the recursive function is called to reverse this array:

$result =  insertToFront($key, reverseArray($value), $result);

The processure of putting an array element to the front of the return array is as below:

function insertToFront($key, $value, $array) {

    $result = [];
    // insert into the front of the result array 
    $result[$key] = $value;

    // append all the rest data
    foreach ($array as $oldKey => $oldValue) {
        $result[$oldKey] = $oldValue;
    }       

   return $result;
}

To test the recursive function reverseArray(array $array), first, let's test with the indexed array:

// Indexed array
$inputArray = [1, 2, 3, 4, 5]; 

echo 'Before Reverse:' . PHP_EOL;
var_dump($inputArray);
echo 'After Reverse:' . PHP_EOL;
var_dump(reverseArray($inputArray));

...

For the rest of the content, please go to the link below:
https://www.codebilby.com/blog/a41-reverse-an-array-in-php-by-using-recursion

PHP functions strcspn() and strspn()

Yongyao Yan — Wed, 04 May 2022 21:10:02 +0000

Function strcspn()

The function strcspn() finds the length of initial segment not matching mask.

In the code snippet below, we want to find the prefix length of a UK post code. CF34 9LH is the post code string and the disallowed character list is 0123456789. The function strcspn() is called to find the length of the initial segment that does not contain any numbers. So, CF is the string segment and the length is 2.

$p = strcspn('CF34 9LH', '0123456789');
echo "The length is " . $p;
//The length is 2

You can then easily get the prefix of a post code like this:

$postCode = 'CF34 9LH';
$postPrefix = substr($postCode, 0, strcspn($postCode, '0123456789'));
echo "The prefix is " . $postPrefix;
//The prefix is CF

You can also use the function strcspn() for checking a file name whether it contains any invalid characters.

$str = "filename123$/@456";
$invalidChars = "\\/*@$";
$validLen = strcspn($str, $invalidChars);

if ($validLen != strlen($str)) {
    echo "Invalid character found at position " . $validLen;
    //Invalid character found at position 11
}

In the above code snippet, since the file name string $str contains invalid characters, the length of the initial segment, i.e. filename123, is not the same with the whole file name string. The error message is therefore printed out.

Fuction strspn()

On the contrary, the function strspn() gets the length of the initial segment of a string, which consists entirely of characters contained within a given mask.
...

For the rest of the content, please go to the link below:
https://www.codebilby.com/blog/a40-php-functions-strcspn-and-strspn

Make Ajax Requests in JavaScript

Yongyao Yan — Tue, 19 Apr 2022 15:24:37 +0000

Ajax is a set of web development techniques on the client side to exchange data with a server asynchronously. It allows updating parts of a web page dynamically without the need of reloading the whole page. In this post, we show you how to make Ajax requests by using jQuery and XMLHttpRequest object.

jQuery

The jQuery JavaScript library allows developers to use Ajax easily.
The jQuery ajax() method is used on the client side to make an Ajax request asynchronously.
To use the jQuery library, we need to reference it with the HTML <script> tag inside the <head> section.

<head>
    <!-- other codes ... -->
    <script src="https://code.jquery.com/jquery-3.5.1.min.js" 
    integrity="sha256-9/aliU8dGd2tb6OSsuzixeV4y/faTqgFtohetphbbj0=" 
    crossorigin="anonymous"></script>
    <!-- other codes ... -->
</head>

By including the jQuery library file from a CDN (Content Delivery Network) as shown above, we don't need to download and host the library file. The integrity and crossorigin attributes are used to verify the resource by using the Subresource Integrity (SRI) checking.

We can add a button on the web page for calling the backend PHP.

<button id="demo">Call PHP</button>

The following JavaScript code block is for the button click event.
When the button is clicked, the jQuery ajax() method will perform an Ajax request to the backend PHP.

<script>
    $(document).ready(function() {
        $("#demo").click(function(){
            var student = {"name":"Tom", "sex":"M", "age":"11", "class":"6Y"};
            $.ajax({
                type: 'POST',
                url: 'my-backend.php',
                data: JSON.stringify(student),
                success: function(data, textStatus, xhr) {
                    alert(data);
                },
                error: function(xhr, textStatus, errorThrown) {
                    alert('Error Msg: ' + errorThrown);
                }
            });        
        });
    });
</script>

The JavaScript variable student defines an object that stores a student's personal data. In the ajax() method, we set the request type to POST. In url, we set the PHP file that will receive the request. The JavaScript function JSON.stringify() is used to convert the object student to a JSON string before it is sent to the server. The functions in success and error will be called respectively when the request succeeds or fails. Here, an alert box with the data returned from the server will display if the request succeeds. If it fails, an alert box will display the textual portion of the HTTP status errorThrown.

In the backend PHP file my-backend.php, we can do like this:

<?php
    $json = file_get_contents('php://input');
    $data = json_decode($json);
    echo $data->name;
?>

The function file_get_contents() is used to get the data sent to the server. The function json_decode() is then called to convert the JSON encoded string $json into a PHP variable $data. Finally, the student's name $data->name is returned to the client side.

XMLHttpRequest object

XMLHttpRequest (XHR) is the other option for developers in Ajax programming. Not just XML, it can be used to fetch any type of data from a server asynchronously. It allows updating parts of a web page without reloading the whole page. To try how it works, just add a button in a web page to trigger a user event to make an Ajax request to the server.

<button id="demo" onclick="makeAjaxCall()">Call PHP</button>

In JavaScript, we make the function makeAjaxCall() to handle the button click event and make an Ajax request by using XMLHttpRequest.

function makeAjaxCall(){
        var request = new XMLHttpRequest();
        request.open('POST', 'my-backend.php');

        var student = {"name":"Tom", "sex":"M", "age":"11", "class":"6Y"};
        request.send(JSON.stringify(student));

        request.onload = function() {
            if (request.readyState == 4) {
                //the operation is done
                if (request.status == 200) {
                    alert(request.response);
                } else if (request.status >= 400){
                    //client or server errors
                    alert('Error Code: ' + request.status + ' Error Msg: ' + request.statusText);
                }

            }

        }

    }

First, the object XMLHttpRequest is initialized.

var request = new XMLHttpRequest();

Then, its method open() is called to create a new request.
The first parameter defines the request method POST. The second parameter is for the URL to send the request to. Here, we set it as the backend PHP file my-backend.php. We define a data object student for storing a student's personal data. The XMLHttpRequest method send() is called to send the request to the server with the data student. The JavaScript function JSON.stringify() is used to convert the object student to a JSON string before it is sent to the server. The XMLHttpRequest onload property is set as a callback function that will be called when the request transaction completes successfully.

After the request is sent, the XMLHttpRequest client will be in the following states:

0 UNSENT
1 OPENED
2 HEADERS_RECEIVED
3 LOADING
4 DONE

In XMLHttpRequest's onload callback function, we can check
the request.readyState property for its state. If it is equal to 4, it means the operation is done. Then, we continue to check the HTTP status code of the XMLHttpRequest's response request.status. If it is equal to 200, it means that the request has succeeded, and we can display the data returned from the server.

alert(request.response);

The HTTP response status codes are grouped in following classes:

Informational responses (100–199)
Successful responses (200–299)
Redirects (300–399)
Client errors (400–499)
Server errors (500–599)

In the JavaScript code snippet above, if the XMLHttpRequest's response status request.status is equal to 400 or over, we will display the error message.

alert('Error Code: ' + request.status + ' Error Msg: ' + request.statusText);

The backend PHP file my-backend.php gets the JSON data posted to the server, decodes it and outputs the student's name $data->name to the client side.

<?php

$json = file_get_contents('php://input');
$data = json_decode($json);
echo $data->name;

?>

References

HTTP response status codes

XMLHttpRequest.readyState

Thanks for reading!
To find more programming tutorials, please visit: CodeBilby.com

Create an array and access array elements in PHP

Yongyao Yan — Sun, 17 Apr 2022 10:15:46 +0000

In PHP, we can create indexed and associative arrays, where integer and string can be used as keys respectively.

Indexed array

You can use the function array() to create an array.

$animal = array("dog", "cat", "sheep", "rabbit", "pig");

In the above example, PHP automatically assigns a numeric index to each element. To print out the details of the array $animal, you can use the function print_r().

print_r($animal);

The above code will output:

Array ( [0] => dog [1] => cat [2] => sheep [3] => rabbit [4] => pig )

As you can see, the index starts from 0 and increase by 1 for each element. You can use the array[key] syntax to access array elements.

print_r($animal[2]);

Output:

sheep

Or you can define your own numeric index explicitly for each array elements.

$animal = array(5=>"dog", 8=>"cat", 9=>"sheep", 14=>"rabbit", 15=>"pig");
print_r($animal);
echo "<br>";
print_r($animal[14]);

The output will be:

Array ( [5] => dog [8] => cat [9] => sheep [14] => rabbit [15] => pig )
rabbit

Associative array

You can also create an array in an associative style, where you can use your own string as a key for each element. With this kind of array, you can store data like using a database.

$student = array("First Name"=>"Emma", "Last Name"=>"Brown", "Age"=>12, "Class"=>"6H");
print_r($student);
echo "<br>";
print_r($student["First Name"]);
echo "<br>";
print_r($student["Age"]);

In the above code snippet, the variable $student stores a student's personal data with different keys: "First Name",
"Last Name", "Age" and "Class".

The output will be:

Array ( [First Name] => Emma [Last Name] => Brown [Age] => 12 [Class] => 6H )
Emma
12

Loop through an array

To iterate over the whole array, PHP's foreach loop is a convenient way.

$student = array("First Name"=>"Emma", "Last Name"=>"Brown", "Age"=>12, "Class"=>"6H");

foreach ($student as $key => $value) {
    echo "{$key}: {$value}<br>";
}

Output:

First Name: Emma
Last Name: Brown
Age: 12
Class: 6H

Create an array of objects

If you want to create an array of objects, you can do like this:

class Car {
    public $brand;
    public $model;
    public $color;
}

$cars = array();
$cars[0] = new Car;
$cars[0]->brand = 'Honda';
$cars[0]->model = 'Jazz';
$cars[0]->color = 'Blue';

$cars[1] = new Car;
$cars[1]->brand = 'Toyota';
$cars[1]->model = 'Yaris';
$cars[1]->color = 'White';

In the above code snippet, class Car is defined followed by the initialization of the array of objects

$cars = array();

Here, we create two sample objects in $cars[0] and $cars[1].
To loop through this array of objects, you can do as follows:

foreach ($cars as $key => $obj) {
    echo "{$key}: {$obj -> brand}<br>";
    echo "{$key}: {$obj -> model}<br>";
    echo "{$key}: {$obj -> color}<br>";
}

The output is:

0: Honda
0: Jazz
0: Blue
1: Toyota
1: Yaris
1: White

Thanks for reading!
To find more programming tutorials, please visit: CodeBilby.com

Set Up Twig for Web Projects in WampServer on Windows

Yongyao Yan — Sun, 17 Apr 2022 09:54:33 +0000

Twig is a popular template engine for PHP programming.
WampServer is a web development environment on Windows, and it allows you to create web applications with Apache, PHP and MySQL. In this post, we will show you how to set up Twig in WampServer on Windows.

1. Install Composer

Go to the website of Composer, the dependency manager for PHP. Download and run the Composer's Windows installer, Composer-Setup.exe. It will install the latest Composer version on your Windows. PHP 5.3.2 is the minimum requirement for Composer to run, while Twig 3.x needs at least PHP 7.2.5. Therefore, we can choose PHP 7.2.10. During the installation, it will ask you the PHP's installation path.
If PHP is under the WampServer folder, you can select its path, for example:

C:\wamp64\bin\php\php7.2.10

By default, the Composer batch file, composer.bat, is installed in the directory as below under Windows 10:

C:\ProgramData\ComposerSetup\bin

Once the installation is complete, the above path is added to the system's path so that
we can run Composer in any directory through Windows command line.

2. Create a new web project in WampServer

It is simple to create a new web project in WampServer.
Go to the WampServer's root directory: C:\wamp64\www.
Create a folder for your web project, for example: C:\wamp64\www\twig-test. Done!

3. Install Twig for your web project

To install Twig, we need to open the Command Prompt in Windows and
change the current directory to the new web project's folder: twig-test

cd C:\wamp64\www\twig-test

After that, install Twig via Composer:

composer require "twig/twig:^3.0"

Then, Twig 3.0.5 is installed under the folder twig-test\vendor.

4. Test the Twig template

First, under the web project folder twig-test, create a subfolder themes for template files. In this folder, we create the template file index.twig as below.

<!DOCTYPE html>
<html>
<head>
    <meta http-equiv="Content-type" content="text/html; charset=utf-8">
    <title>Testing the Twig Template</title>
</head>
<body>
    <h1>Hello world</h1>
    <p>I love {{ fruit }} !</p>
</body>
</html>

In the above code, fruit is the variable passed to the template.
The double-curly-brace {{}} is used to print out the value of the variable fruit.

Second, under the folder twig-test, create a PHP file test.php to render the template.

<?php
require_once './vendor/autoload.php';

$loader = new \Twig\Loader\FilesystemLoader('./themes');

$twig = new \Twig\Environment($loader);

echo $twig->render('index.twig', array("fruit" => "watermelon"));

?>

In the above code, first, Composer's PHP file autoload.php is included to map the Twig's namespaces to real folders. The loader \Twig\Loader\FilesystemLoader is then created to look up templates in the ./themes directory. The \Twig\Environment object, $twig, is initialized with default configurations. The template file index.twig is finally loaded and rendered with an array as the parameter. In the array array("fruit" => "watermelon"), the variable fruit and its value are defined.

To check the result, open an Internet browser and access the PHP file test.php. For example, in the address bar, type http://localhost/twig-test/test.php. You will see that the template file is rendered and the variable's value watermelon is passed to the template.

Thanks for reading!
To find more programming tutorials, please visit: CodeBilby.com

Render a DateTime Object in Twig

Yongyao Yan — Sun, 17 Apr 2022 09:17:17 +0000

The date filter

In Twig, the date filter uses the same DateTime format of PHP
to render DateTime instances in server-side.

require_once './vendor/autoload.php';

$loader = new \Twig\Loader\FilesystemLoader('./themes');

$twig = new \Twig\Environment($loader);

$twig->getExtension(\Twig\Extension\CoreExtension::class)->setTimezone('Australia/Melbourne');

$dt = new DateTime("2010-07-05 06:00:00", new DateTimeZone("Australia/Melbourne"));

echo $twig->render('render-a-datetime.twig', array("myDateTime" => $dt));

In the above PHP code snippet, the function setTimezone is used to set the default timezone globally in Twig. The new DateTime instance $dt is created with the timezone of Australia/Melbourne. After that, it is passed to the template file render-a-datetime.twig. In the template file, we can render the DateTime variable myDateTime like this:

{{ myDateTime|date("d M Y H:i") }}

The output will be:

05 Jul 2010 06:00

If want to show the current date in Twig, we can use the word now.

{{ "now"|date("d M Y H:i") }}

The date filter with a timezone

We can override the default timezone in the date filter with a given timezone string. For the details of the supported timezones, you can refer to List of Supported Timezones. For example, you can display the current date instance for different cities.

<p>
   New York: {{ "now"|date("d M Y H:i", "America/New_York") }} <br>
   Paris: {{ "now"|date("d M Y H:i", "Europe/Paris") }} <br>
   Hong Kong: {{ "now"|date("d M Y H:i", "Asia/Hong_Kong") }} <br>
   Melbourne: {{ "now"|date("d M Y H:i", "Australia/Melbourne") }}
</p>

The above code will output:

New York: 20 Oct 2020 20:30
Paris: 21 Oct 2020 02:30
Hong Kong: 21 Oct 2020 08:30
Melbourne: 21 Oct 2020 11:30

Thanks for reading!
To find more programming tutorials, please visit: CodeBilby.com

String Concatenation and Interpolation in Twig

Yongyao Yan — Sun, 17 Apr 2022 08:55:43 +0000

Twig has two useful operations, ~ and #{}, for string concatenation and interpolation respectively.

String concatenation

We can use the operator ~ to convert all operands into strings and append one string to the end of another. For example, in PHP, we pass two variables to the template string.twig.

echo $twig->render('string.twig', array("numA" => "1", "numB" => "9"));

In the template file string.twig, we can use the operator ~ to concatenate the strings.

<P>{{ "Number A is: " ~ numA}}<br>
   {{ "Number B is: " ~ numB}}
</p>

The output will be:

Number A is: 1
Number B is: 9

String interpolation

Within a double-quoted string, we can use the interpolation operator #{} to evaluate a valid expression and the result is converted to a string for display. In the template file, we can do like this:

<P>
   {{ "A + B = #{numA + numB}"}}
</p>

The numbers numA and numB will be added together, and the output will be:

A + B = 10

Thanks for reading!
To find more programming tutorials, please visit: CodeBilby.com

Write Your Own Filters and Functions in Twig

Yongyao Yan — Sat, 16 Apr 2022 13:34:19 +0000

Twig provides a flexible way to make extensions.
By implementing the Twig AbstractExtension class, you can create your own custom filters and functions that can be used in templates.

Create your own filters

For example, if we want to create filters bold and italic that make the characters on a web page become bold and italic, respectively like this:

{{ "Bold string"|bold }}

{{ "Italic string"|italic }}

Then we can create a new class that extends AbstractExtension and implement the function getFilters():

//MyExtension.php

use \Twig\Extension\AbstractExtension;
use \Twig\TwigFilter;

class MyExtension extends AbstractExtension {
    public function getFilters() {
        return [
            new TwigFilter('bold', [$this, 'makeBold']),
            new TwigFilter('italic', [$this, 'makeItalic']),
        ];
    }

    public function makeBold($str) {
        return '<b>'.$str.'</b>';
    }

    public function makeItalic($str) {
        return '<i>'.$str.'</i>';
    }    

}

In the above code snippet, we return two TwigFilter objects
for filters bold and italic in the function getFilters().
Functions makeBold($str) and makeItalic($str) implement the logic for
making characters to be bold and italic in HTML code.

Create your own functions

If you want to create a function, implement the function getFunctions() like this:

//MyExtension.php

use \Twig\Extension\AbstractExtension;
use \Twig\TwigFilter;
use \Twig\TwigFunction;

class MyExtension extends AbstractExtension {
    public function getFilters() {
        return [
            new TwigFilter('bold', [$this, 'makeBold']),
            new TwigFilter('italic', [$this, 'makeItalic']),
        ];
    }

    public function getFunctions() {
        return [
            new TwigFunction('getArea', [$this, 'getArea']),
        ];
    }

    public function makeBold($str) {
        return '<b>'.$str.'</b>';
    }

    public function makeItalic($str) {
        return '<i>'.$str.'</i>';
    }    

    public function getArea($len) {
        return $len * $len;
    }
}

In the above code snippet, we return a new TwigFunction object for calculating the area of a square
in the function getFunctions(). The detail logic is defined in the function getArea($len).

How to use

To test the new created Twig extensions, we can do like this:

require_once './vendor/autoload.php';
require_once 'MyExtension.php';

$loader = new \Twig\Loader\FilesystemLoader('./themes');

$twig = new \Twig\Environment($loader, ['autoescape' => false]);

$twig->addExtension(new MyExtension());

echo $twig->render('test-extension.twig', array("len" => "9"));

First, Composer's PHP file autoload.php is included to map the Twig's namespaces to real folders. In order to insert the HTML code into the template when using our new created filters, we need to disable the autoescape option when initializing the Twig Environment. Then, we add the new created extension MyExtension. Finally, we render the template test-extension.twig by passing the length of one side of a square, len.

In the template test-extension.twig, we can call bold, italic and getArea() as below:

<h1>{{ "Twig Extension Demo"|italic }}</h1>
<p>
If the length of one side of a square is {{ len|bold }} meter, 
the area of the square is {{ getArea(len)|bold }} square meters.
</p>

After rendering, the web page will look like:

Thanks for reading!
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