Php Coding Practices
The Basics
PHP is a vast language that allows coders of all levels the ability to produce code not only quickly, but efficiently. However while advancing through the language, we often forget the basics that we first learnt (or overlooked) in favor of short cuts and/or bad habits. To help combat this common issue, this section is aimed at reminding coders of the basic coding practices within PHP.
Continue reading on The Basics
Date and Time
PHP has a class named DateTime to help you when reading, writing, comparing or calculating with date and time. There are many date and time related functions in PHP besides DateTime, but it provides nice object-oriented interface to most common uses. It can handle time zones, but that is outside this short introduction.
To start working with DateTime, convert raw date and time string to an object with createFromFormat() factory method or do new DateTime to get the current date and time. Use format() method to convert DateTime back to a string for output.
<?php
$raw = '22. 11. 1968';
$start = DateTime::createFromFormat('d. m. Y', $raw);
echo 'Start date: ' . $start->format('Y-m-d') . "\n";
Calculating with DateTime is possible with the DateInterval class. DateTime has methods like add() and sub() that take a DateInterval as an argument. Do not write code that expect same number of seconds in every day, both daylight saving and timezone alterations will break that assumption. Use date intervals instead. To calculate date difference use the diff() method. It will return new DateInterval, which is super easy to display.
<?php
// create a copy of $start and add one month and 6 days
$end = clone $start;
$end->add(new DateInterval('P1M6D'));
$diff = $end->diff($start);
echo 'Difference: ' . $diff->format('%m month, %d days (total: %a days)') . "\n";
// Difference: 1 month, 6 days (total: 37 days)
On DateTime objects you can use standard comparison:
<?php
if ($start < $end) {
echo "Start is before end!\n";
}
One last example to demonstrate the DatePeriod class. It is used to iterate over recurring events. It can take two DateTime objects, start and end, and the interval for which it will return all events in between.
<?php
// output all thursdays between $start and $end
$periodInterval = DateInterval::createFromDateString('first thursday');
$periodIterator = new DatePeriod($start, $periodInterval, $end, DatePeriod::EXCLUDE_START_DATE);
foreach ($periodIterator as $date) {
// output each date in the period
echo $date->format('Y-m-d') . ' ';
}
Read about DateTime
Read about date formatting (accepted date format string options)
Design Patterns
When you are building your application it is helpful to use common patterns in your code and common patterns for the overall structure of your project. Using common patterns is helpful because it makes it much easier to manage your code and lets other developers quickly understand how everything fits together.
If you use a framework then most of the higher level code and project structure will be based on that framework, so a lot of the pattern decisions are made for you. But it is still up to you to pick out the best patterns to follow in the code you build on top of the framework. If, on the other hand, you are not using a framework to build your application then you have to find the patterns that best suit the type and size of application that you’re building.
Continue reading on Design Patterns
Working with UTF-8
This section was originally written by Alex Cabal over at PHP Best Practices and has been used as the basis for our own UTF-8 advice.
There’s no one-liner. Be careful, detailed, and consistent.
Right now PHP does not support Unicode at a low level. There are ways to ensure that UTF-8 strings are processed OK, but it’s not easy, and it requires digging in to almost all levels of the web app, from HTML to SQL to PHP. We’ll aim for a brief, practical summary.
UTF-8 at the PHP level
The basic string operations, like concatenating two strings and assigning strings to variables, don’t need anything special for UTF-8. However most string functions, like strpos() and strlen(), do need special consideration. These functions often have an mb_* counterpart: for example, mb_strpos() and mb_strlen(). These mb_* strings are made available to you via the Multibyte String Extension, and are specifically designed to operate on Unicode strings.
You must use the mb_* functions whenever you operate on a Unicode string. For example, if you use substr() on a UTF-8 string, there’s a good chance the result will include some garbled half-characters. The correct function to use would be the multibyte counterpart, mb_substr().
The hard part is remembering to use the mb_* functions at all times. If you forget even just once, your Unicode string has a chance of being garbled during further processing.
Not all string functions have an mb_* counterpart. If there isn’t one for what you want to do, then you might be out of luck.
You should use the mb_internal_encoding() function at the top of every PHP script you write (or at the top of your global include script), and the mb_http_output() function right after it if your script is outputting to a browser. Explicitly defining the encoding of your strings in every script will save you a lot of headaches down the road.
Additionally, many PHP functions that operate on strings have an optional parameter letting you specify the character encoding. You should always explicitly indicate UTF-8 when given the option. For example, htmlentities() has an option for character encoding, and you should always specify UTF-8 if dealing with such strings. Note that as of PHP 5.4.0, UTF-8 is the default encoding for htmlentities() and htmlspecialchars().
Finally, If you are building a distributed application and cannot be certain that the mbstring extension will be enabled, then consider using the patchwork/utf8 Composer package. This will use mbstring if it is available, and fall back to non UTF-8 functions if not.
UTF-8 at the Database level
If your PHP script accesses MySQL, there’s a chance your strings could be stored as non-UTF-8 strings in the database even if you follow all of the precautions above.
To make sure your strings go from PHP to MySQL as UTF-8, make sure your database and tables are all set to the utf8mb4 character set and collation, and that you use the utf8mb4 character set in the PDO connection string. See example code below. This is critically important.
Note that you must use the utf8mb4 character set for complete UTF-8 support, not the utf8 character set! See Further Reading for why.
UTF-8 at the browser level
Use the mb_http_output() function to ensure that your PHP script outputs UTF-8 strings to your browser.
The browser will then need to be told by the HTTP response that this page should be considered as UTF-8. The historic approach to doing that was to include the charset <meta> tag in your page’s <head> tag. This approach is perfectly valid, but setting the charset in the Content-Type header is actually much faster.
<?php
// Tell PHP that we're using UTF-8 strings until the end of the script
mb_internal_encoding('UTF-8');
// Tell PHP that we'll be outputting UTF-8 to the browser
mb_http_output('UTF-8');
// Our UTF-8 test string
$string = 'Êl síla erin lû e-govaned vîn.';
// Transform the string in some way with a multibyte function
// Note how we cut the string at a non-Ascii character for demonstration purposes
$string = mb_substr($string, 0, 15);
// Connect to a database to store the transformed string
// See the PDO example in this document for more information
// Note the `charset=utf8mb4` in the Data Source Name (DSN)
$link = new PDO(
'mysql:host=your-hostname;dbname=your-db;charset=utf8mb4',
'your-username',
'your-password',
array(
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
PDO::ATTR_PERSISTENT => false
)
);
// Store our transformed string as UTF-8 in our database
// Your DB and tables are in the utf8mb4 character set and collation, right?
$handle = $link->prepare('insert into ElvishSentences (Id, Body) values (?, ?)');
$handle->bindValue(1, 1, PDO::PARAM_INT);
$handle->bindValue(2, $string);
$handle->execute();
// Retrieve the string we just stored to prove it was stored correctly
$handle = $link->prepare('select * from ElvishSentences where Id = ?');
$handle->bindValue(1, 1, PDO::PARAM_INT);
$handle->execute();
// Store the result into an object that we'll output later in our HTML
$result = $handle->fetchAll(\PDO::FETCH_OBJ);
header('Content-Type: text/html; charset=UTF-8');
?><!doctype html>
<html>
<head>
<meta charset="UTF-8">
<title>UTF-8 test page</title>
</head>
<body>
<?php
foreach($result as $row){
print($row->Body); // This should correctly output our transformed UTF-8 string to the browser
}
?>
</body>
</html>
Further reading
- PHP Manual: String Operations
- PHP Manual: String Functions
- PHP Manual: Multibyte String Functions
- PHP UTF-8 Cheatsheet
- Handling UTF-8 with PHP
- Stack Overflow: What factors make PHP Unicode-incompatible?
- Stack Overflow: Best practices in PHP and MySQL with international strings
- How to support full Unicode in MySQL databases
- Bringing Unicode to PHP with Portable UTF-8
- Stack Overflow: DOMDocument loadHTML does not encode UTF-8 correctly
