php-for-wordpress

PHP for WordPress

• What is PHP
• Basic Concepts
• Variables
• WordPress PHP Coding Standards
• The Loop
• Template Tags
• Conditional Tags
• WordPress Hooks

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.

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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.

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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.

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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.

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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; ?>

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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()

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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()

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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.

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