Before going to into the details of WordPress Coding Standards, you need to know the purpose of the coding standards & why you need to have coding standards. In this blog, we will focus on part 1 – WordPress Coding Standards For PHP & HTML and in the next blog, we will focus on part 2 – WordPress Coding Standards For CSS & JS.

1. In-Depth Guide On WordPress Coding Standards For
PHP, HTML
“ANY FOOL CAN WRITE A CODE THAT COMPUTER CAN UNDERSTAND. GOOD
PROGRAMMERS WRITE CODE THAT HUMAN CAN UNDERSTAND.”
- JOHN JOHNSON
This quote is good enough to understand the importance of standards as far as the coding is
concerned. Every programming language has its own rules and regulations for the coding which is
also known as the coding standards.
Each programmer should follow these coding standards in order to inherit the best practices in
his/her professional career. Coding standards are not the syntax that strictly needs to be followed,
they are more of coding conventions that if followed by the programmer can help them to enhance
their coding style.
The same applies to the case of WordPress where it has its own coding standards which every
developer should have the knowledge of. Taking this into consideration, we have developed a
two-part series on WordPress Coding Standards which will help you to know the coding standards
for PHP, HTML, CSS, & JS.
Here’s how we will progress right through the WordPress Coding Standards series:

2. Part 1: In-Depth Guide On WordPress Coding Standards For PHP & HTML
Part 2: In-Depth Guide On WordPress Coding Standards For CSS & JS
In this blog, we will focus on part 1 - WordPress Coding Standards For PHP & HTML and in the
next blog, we will focus on part 2 - WordPress Coding Standards For CSS & JS.
Before going to into the details of WordPress Coding Standards, you need to know the purpose of
the coding standards & why you need to have coding standards.
What Is The Purpose Of WordPress Coding Standards?
The sole purpose of the WordPress Coding Standards is to create a base for collaboration and
review within the various aspects of WordPress open-source project & community right from the
core part to the themes and plugins.
Why You Need Coding Standards?
Coding standards help you to avoid common errors, simplify the modification process & most
importantly assists you in improving the readability of your code.
In addition to all these, the coding standards ensure that all files within one project appear as if
they’re created by a single person.
Another major advantage you get by following the coding standards is that anyone will be able to
understand your code and also modify it, without contacting you.
So, if you’re planning to develop a website in WordPress, you should know the coding standards.
Now, let’s dive deep into the core part & understand the various coding standards.

3. Part 1: In-Depth Guide On WordPress Coding
Standards For PHP & HTML:-
WordPress Coding Standards For PHP
1. Using Single & Double Quotes
If you’re someone who is working in a Custom WordPress Development Company, then you
must be knowing that appropriate use of single and double quotes is necessary.
As per the standard convention if you’re not evaluating anything in the string, then you should use
the single quotes. Otherwise, you should always prefer using the double quotes for the string value
while writing PHP code for the WordPress platform.
Example:
echo '<a href="www.url.com" title="Contact">Contact Us</a>';
echo "<a href='$cta_link' title='$cta_title'>$cta_label</a>";
Here, we have used double quotes for displaying the “Contact” as it is a value for the title attribute,
while we have used a single quote for ‘$cta_title’ as we’re not evaluating its value.
2. Indentation
Another very important thing that you need to remember while writing the code in PHP is the
proper use of indentation. The reason behind that is, it always reflects the logical structure of your
code. Always use tabs for indentation instead of space, as it improves readability.
However, there is one exception: If you've got a block of code which looks more readable if the
code is written in an aligned manner, then you can use space for that purpose.
Example:
[tab]'demo' => 'demovalue';
[tab]'demo1' => 'demovalue1’;
[tab]'demo2' => 'demovalue2';
[tab]'demo3' => 'demovalue3';
For associative arrays, each item should start on a new line when the array contains more than one
item:

4. Example:
$key_value_array = array(
[tab]'demo' => 'demovalue',
[tab]'demo1' => 'demovalue1',
[tab]'demo2' => 'demovalue2',
[tab]'demo3' => 'demovalue3',
);
Here, you may have noted a comma after the last item. This is recommended by the WordPress as
it makes it easier for you to change the order of an array.
Example:
[tab]'demo3' => 'demovalue3',
[tab]'demo1' => 'demovalue1',
[tab]'demo' => 'demovalue',
[tab]'demo2' => 'demovalue2',
);
For the switch structures, the case should be indented one tab from the switch statement and
break should be one tab from the case statement.
Example:
switch ( $condition ) {
[tab]case 'value':
[tab][tab]demo_function();
[tab][tab]break;
[tab]case 'value2':
[tab][tab]demo_function1();
[tab][tab]break;
}
As a thumb rule, Tabs should be used at the beginning of the line for indentation and Space should
be used for the mid-line alignment.
3. Brace Style
Braces should be used for all the blocks as shown in the snippet below:
Example:

5. if ( condition ) {
function();
function2();
} elseif ( condition2 && condition3 ) {
function3();
function4();
} else {
defaul_function();
}
In case, you have a really long block, it can be broken into 2 or more shorter blocks to reduce
complexity and improve readability.
Example:
if ( condition ) {
function();
function2();
} elseif ( condition2 && condition3 ) {
function3();
function4();
} else {
defaul_function();
}
foreach ( $data as $data_key => $data_value ) {
echo $data_value;
}
One thing that should be noted here is that the use of braces is to avoid single-statement inline
control structures. You’re free to use the alternative syntax for control structure, especially when
the PHP code is embedded into the HTML.
Example:
<?php if ( !empty( $data ) ) { ?>
<div class="test">
<?php foreach ( $data as $data_key => $data_value ) { ?>
<div id="data-<?php echo $data_key; ?>">
<!-- Other Content -->
</div>
<?php } ?>
</div>
<?php } ?>

6. 4. Use elseif, Not else if
else if is not compatible with the colon-based syntax for if|elseif blocks. Therefore, you should
always use elseif instead of using else if.
5. Multiline Function Calls
As a WordPress developer, when you split the function call over the multiple lines, always
remember to keep each parameter on a separate line.
Each parameter should not consume more than one line and multiline parameter values must be
assigned to a variable, so you just need to pass that variable to the function call.
Example:
```
$bar = array(
'use_this' => true,
'meta_key' => 'field_name',
);
$baz = sprintf(
/* translators: %s: Friend's name */
esc_html__( 'Hello, %s!', 'yourtextdomain' ),
$friend_name
);
$a = foo(
$bar,
$baz,
/* translators: %s: cat */
sprintf( __( 'The best pet is a %s.' ), 'cat' )
);
6. Regular Expressions
Always use Perl compatible regular expressions (PCRE) with the reference to their POSIX
counterparts. Never use the /e switch, use preg_replace_callback instead. In addition to all these,
you should always use single-quoted strings for the regular expressions.
7. Opening & Closing PHP Tags
When you’re embedding multiline PHP snippets within an HTML block, the PHP open and close
tags must be on a line by themselves.

7. Example: (multiline)
function test_function() {
?>
<div>
<?php
echo '<a href="www.url.com" title="Contact">Contact Us</a>';
?>
</div>
<?php
}
Example: (single line)
<input type="text" name="<?php echo $name ; ?>" />
8. No Shorthand PHP Tags
Never use shorthand PHP tags, always use full PHP tags.
Example: (Incorrect)
```
<? ... ?>
<?= $var ?>
Example: (Correct)
```
<?php ... ?>
<?php echo $var; ?>
9. Remove Trailing Spaces
Always remember to remove the trailing whitespaces at the end of your each coding line. You
should omit the PHP tag at the end of the file. However, if you’re using the tag, then don’t forget to
remove the trailing whitespace.
10. Proper Usage Of Space
Always put space after every comma and also on both sides of logical, comparison, string and
assignment operators.
Example:

8. y == 2
foo && bar
! foo
array( 1, 2, 3 )
$baz . '-4'
$term .= 'Z'
Remember to put spaces on both sides opening and closing parentheses of if, elseif, foreach, for,
and switch blocks.
Example:
```
foreach ( $foo as $bar ) { …
Also, follow this rule while defining a function.
Example:
function dummy( $param1 = 'foo', $param2 = 'bar' ) { ...
function my_dummy_function1() { ...
When you’re calling any function, you need to follow the rule mentioned above.
Example:
first_function1( $param1, func_param( $param2 ) );
my_dummy_function();
For logical comparisons, the same rule applies.
Example:
```
if ( ! $foo ) { ...
When you’re performing typecasting, the above rule is also valid.
Example:
```
foreach ( (array) $foo as $bar ) { ...

9. $foo = (boolean) $bar;
When referring to array items, include a space around the index only if it’s variable.
Example:
$x = $foo['bar']; // correct
$x = $foo[ 'bar' ]; // incorrect
$x = $foo[0]; // correct
$x = $foo[ 0 ]; // incorrect
$x = $foo[ $bar ]; // correct
$x = $foo[$bar]; // incorrect
For a switch block, there should be any space before the colon for a case statement.
Example:
```
switch ( $foo ) {
case 'bar': // correct
case 'ba' : // incorrect
}
Similarly, there should be no space before the colon on the return type declaration.
Example:
```
function sum( $a, $b ): float {
return $a + $b;
}
11. Formatting SQL Statements
When you’re formatting any SQL statement, you should break it into several lines and indent if it’s
sufficiently complex. Always capitalize the SQL parts of the statements such as WHERE or
UPDATE.
Functions that update the database should expect their parameters to lack SQL slash escaping
when passed. For that purpose, escaping should be done by using $wpdb->prepare().
$wpdb->prepare() is a method that handles escaping, quoting and int-casting for SQL queries.

10. Example:
<?php
// set the meta_key to the appropriate custom field meta key
$meta_key = 'miles';
$allmiles = $wpdb->get_var( $wpdb->prepare(
"
SELECT sum(meta_value)
FROM $wpdb->postmeta
WHERE meta_key = %s
",
$meta_key
) );
echo "<p>Total miles is {$allmiles}</p>";
?>
Here, %s is used for string placeholders and %d is used for integer placeholders. Note that they
are not ‘quoted’! $wpdb->prepare() will take care of escaping and quoting for us. This is the
benefit you get if you utilize this function.
12. Database Queries
Always avoid touching the database in a direct manner. Utilize the functions for extracting the data
whenever possible. The reason behind that is, Database Abstraction (using functions in place of
queries) helps you to keep your code forward-compatible.
13. Naming Conventions
Always use lowercase for a variable, action/filter, and function names. Separate the words by
using underscore. In addition to that, choose a name which is unambiguous & self-documenting.
Example:
function some_name( $some_variable ) { [...] }
For class name, you should use capitalize words which are separated by underscores.
Example:
```
class Walk_Categorization extends Walk { [...] }
All the constants should be in upper-case with words being separated by underscores.

11. Example:
```
define( 'PI', true );
The file should be named descriptively by using the lowercase and for separating the words you
should utilize hyphen.
My-new-theme.php
For class file name should be based on the class name i.e. class- followed by a hyphen.
Example:
If the class name is class Walk_Categorization, then the class file name should be
class-walk-categroization.php
There is one exception in the class file name for three files: class.wp-dependencies.php,
class.wp-scripts.php, class.wp-styles.php. These files are ported into Backpress and therefore,
they are prepended with class. instead of a hyphen.
14. Self-Explanatory Flag Values for Function Arguments
Always prefer using true & false for the string values when you're calling a function.
Example:
// Incorrect
function eat( $what, $slowly = true ) {
...
}
eat( 'wheat', true );
eat( 'rice', false );
Now, PHP doesn’t support flag arguments and therefore, sometimes the values of flags are
meaningless as it is in our example shown above. So, for that type of scenario, you should make
your code readable by utilizing descriptive string values instead of booleans.
Example:
// Correct
function eat( $what, $slowly = ‘slowly’) {
...
}

12. eat( 'wheat', ‘slowly’ );
eat( 'rice', ‘quickly’ );
15. Interpolation for Naming Dynamic Hooks
For naming the dynamic hooks, you should utilize the interpolation methodology rather than using
the concatenation for readability purpose. Dynamic hooks are the one which includes dynamic
values in their tag name - {$new_status}_{$post->post_type} (publish_post).
Always include the variables of your hook tags inside the curly braces {} and the outer tag name
should be wrapped in double quotes. The reason behind following this methodology is to ensure
that PHP can correctly parse the variable types with interpolated string:
Example:
```
do_action( "{$new_status}_{$post->post_type}", $post->ID, $post );
16. Ternary Operator
For using the ternary operator, always have them test if the statement is true, not false. Otherwise,
it can create a massive confusion in the future.
Example:
```
$musictype = ( 'jazz' == $music ) ? 'cool' : 'blah';
17. Yoda Conditions
When you’re doing the logical comparisons which include variables, always put the variable on
the right-hand side & constants, literals, or function calls on the left-hand side. If neither side has a
variable, then the order is not that important.
Example:
```
if ( true == $the_force ) {
$victorious = you_will( $be );
}
Here, if you omit an equals sign (=), then you will get a parse error, as you can’t assign a value to
constant like true. Instead of that, if you’ve written ( $the_force = true ), the assignment would be

13. perfect and you won’t get an error. This is known as the Yoda Condition and it applies to ==, !=,
===, !==, <, >, <= or >= operators.
18. Clever Coding
For coding, readability is more important than cleverness.
Example:
```
isset( $var ) || $var = some_function();
This might look clever, but it has low readability. Instead of that, if you write:
if ( ! isset( $var ) ) {
$var = some_function();
}
Then, the readability improves drastically.
In the case of a switch statement, it’s ok to have multiple cases in a common block. However, if a
case contains a block, the falls through to the next block, then this should be explicitly commented
as shown in the snippet below:
switch ( $foo ) {
case 'bar': // Correct, an empty case can fall through without comment.
case 'baz':
echo $foo; // Incorrect, a case with a block must break, return, or
have a comment.
case 'cat':
echo 'mouse';
break; // Correct, a case with a break does not require a comment.
case 'dog':
echo 'horse';
// no break // Correct, a case can have a comment to explicitly mention
the fall-through.
case 'fish':
echo 'bird';
break;
}
WordPress Coding Standards For HTML
1. Validation

14. All the HTML pages should be verified with the help of the W3C Validator to ensure that markup
is well-formed. Although this is not the only indicator of good coding, it helps to solve the
problems that are to be tested via the automation process. The manual code review cannot be as
effective as this one and that’s why it is recommended that you should validate your code.
2. Self-Enclosing Elements
All tags must be properly closed. Howver, for the tags that are self-enclosing, the forward slash
should have once space preceding it.
Example:
```
<br /> //Correct
<br/> //Incorrect
3. Attributes & Tags
All the tags, as well as their attributes, must be written in lowercase. In addition to that, attribute
values should be in lowercase when the purpose of the text is just to be interpreted by a machine.
However, when an attribute value is going be read by a human, proper capitalization should
follow:
Example:
<meta http-equiv="content-type" content="text/html; charset=utf-8" /> // For
Machine
<a href="http://abc.com/" title="Content Writer">ABC.com</a> // For Human
4. Quotes
As per the W3C specification for XHTML, all the attributes must have a value & must be wrapped
inside single or double quotes.
Example:
```
<input type="text" name="ABC" disabled="disabled" /> //Correct
<input type='text' name=’ABC’ disabled='disabled' /> //Correct
<input type=text name=email disabled>//Incorrect

15. Howver, in HTML all attributes do not have to have values & they do not have to be quoted. But
you should follow these conventions to avoid any kind of security vulnerabilities.
5. Indentation
Like PHP, HTML indentation should always reflect logical structure. So always use tabs and not
spaces. If you’re mixing PHP & HTML, then indent PHP blocks to match the HTML code.
Example:
?php if ( ! have_posts() ) : ?>
<div id="post-1" class="post">
<h1 class="entry-title">Not Found</h1>
<div class="entry-content">
<p>Apologies, but no results were found.</p>
<?php get_search_form(); ?>
</div>
</div>
<?php endif; ?>
Final Thoughts…
Every programming language has its own coding standards which need to be followed by the
programmer in order to enhance the readability of the code. The same is the case with WordPress,
where there are coding standards for PHP, HTML, CSS & JS.
Here, we have tried to provide you with an in-depth guide on WordPress Coding Standards For
PHP & HTML which will help you in future when you're developing something in WordPress.
If you’ve any question or suggestion regarding this subject, then do mention them in our comment
section. Thank You!
Originally Published at esparkinfo.com