Skip to content

Latest commit

 

History

History
212 lines (169 loc) · 7.24 KB

README.md

File metadata and controls

212 lines (169 loc) · 7.24 KB

PHP for WordPress

What is PHP

PHP (PHP HyperText Preprocessor) is a server side programming language. This means that our PHP is processed on the server running our website, whether that is locally or with a hosting service. Once PHP is executed, it generates HTML files and served them to the browser.

  • PHP is a programming language.
  • WordPress itself is built largely with PHP.
  • PHP runs on the server before HTML is sent to browser.
  • PHP can be used outside of WordPress as well.


Basic Concepts

  • PHP files end with the extension .php. This means they can include PHP code. However, they can also include HTML code as well.
  • Although PHP files can include PHP, all PHP must be wrapped inside a PHP block <?php ... ?>
  • Variables is the way to temporarily store values in memory. The variables names start with a dollar sign $ and should use an _ (underscore) rather than spaces or camelCase style.
  • Echo is a function for us to display something on the page with PHP. When we have an arry or object saved as variables, we may have to use var_export to display the values.
  • Arrays are variables that store multiple values. To create an array, we use [] and separate each value with a comma ,.
  • Foreach Loop will let us repeat a set of actions on each item in an array.
  • Functions let us write and reuse blocks of code. A function contains two parts: (1) function declaration and (2) function body.


Variables

<?php
  $first_name = "Da-Ming";
  $last_name = "Wang";
?>

<h2>Welcome!</h2>
<p>My name is "<?php echo $first_name . " " . $last_name; ?>."</p>
  • A variable starts with a dollar sign $, followed by the name of the variable.
  • Don't forget the semi-colon ; at the end of every line.
  • We can use period character . to concatenate strings.


WordPress PHP Coding Standards

  • Use single and double quotes when appropriate.
  • Use real tabs and not spaces for indentation.
  • Braces should always be used, even when they are not required.
  • Use elseif instead of else if.
  • Use long array syntax array( 1, 2, 3 ) for declaring arrays more readable.
  • Not shorthand PHP tags <? ...?>.
  • Always put spaces after commas, and on both sides of logical, comparison, string and assignment operations.
  • Use lowercase letters in variable, action and function names. Separate words via underscores.
  • Class names should use capitalized words separated by underscores. Any acronyms should be all upper case.
  • Constants should be in all upper-case with underscores separating words.
  • Files should be named descriptively using lowercase letters. Hyphens should separate words.
  • Class file names should be based on the class name with class- prepended and the underscores in the class name replaced with hyphens.
  • Always have Tenary operators if the statement is true.
  • Use Yoda Conditions (always put the variable on the right side and put constants, literals or function calls on the left side).

Visit PHP Coding Standards | WordPress Developer for more information.



The Loop

<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
  <h1><?php the_title(); ?></h1>
  <?php the_content(); ?>
<?php endwhile; else: ?>
  <p><?php _e( "Sorry, no content available!", "textdomain" ); ?></p>
<?php endif; ?>


Template Tags

The Template Tags are special functions that allow us to easily get information and content from WordPress. Here are a few examples of the many different template tags that are available.

  • get_header()
  • get_footer()
  • get_sidebar()
  • get_template_part()
  • get_the_title()
  • the_title()
  • the_content()
  • the_author()`
  • the_category()
  • the_tags
  • the_post_thumbnail()
  • the_permalink()()
  • edit_post_link()
  • site_url()
  • wp_nav_menu()
  • wp_login_form()
  • bloginfo()
  • comment_author()


Conditional Tags

The Conditional Tags are WordPress functions that return true when certain conditions are met. ere are a few examples of the many different conditional tags that are available.

  • is_front_page()
  • is_home()
  • is_admin()
  • is_single()
  • is_single('slug')
  • is_single(['slug-1'], ['slug-2'])
  • is_singular()
  • get_post_type()
  • has_excerpt()
  • is_page()
  • is_page('slug')
  • is_page(['slug-1', 'slug-2'])
  • is_page_template('custom.php')
  • comments_open()
  • is_category()
  • is_tag()
  • is_archive()
  • in_the_loop()


WordPress Hooks

The Hooks allow us to add custom code into existing software (e.g. WordPress). There're two different types of hooks in WordPress:

  • Action Hooks let us run our own code when certain events take place in the WordPress run cycle.

    function phpforwp_theme_styles() {
  // Enqueue google fonts https://fonts.googleapis.com/css?family=Open+Sans|Varela+Round
  wp_enqueue_style( 'font-css', 'https://fonts.googleapis.com/css?family=Open+Sans|Varela+Round' );
  
  // Enque main style sheet (make dependent on google fonts)
  wp_enqueue_style( 'main-css', get_stylesheet_uri(), [ 'font-css' ], get_the_time() );
}

// Add phpforwp_theme_styles function to wp_enqueue_scripts action hook with a priority of 10
add_action( 'wp_enqueue_scripts', 'phpforwp_theme_styles', 10 );

  • Filter Hooks let us modify how content is displayed on a page or saved to the database.

    function phpforwp_read_more_link( $excerpt ) {

  // Create a variable called $extended_excerpt and assign it the value of $excerpt
  $extended_excerpt = $excerpt;

  // Append a read more link using get_permalink() as the url
  $extended_excerpt .= ' <a href="' . get_permalink() . '">';
  $extended_excerpt .= 'Read more &raquo;';
  $extended_excerpt .= '</a>';

  // Return $extended_excerpt
  return $extended_excerpt;

}
// Add phpforwp_read_more_link function to the get_the_excerpt with a priority of 10
add_filter( 'get_the_excerpt', 'phpforwp_read_more_link', 100 );

So the hooks are generally used in plugin files or the functions.php file in themes, not in the template files.