Entry-level PHP for WordPress

Who is this for?
You can read HTML
You know how to access WordPress
theme ﬁles via FTP
You’ve seen some of these things  
( <?php ?>) and you want to know
what they do

Where is this magical PHP?
Theme ﬁles
Plugin ﬁles

Tools
Not the WordPress ﬁle editor!
Atom 
Sublime Text 2
Coda 2
Any IDE will do

<?php if (have_posts()) : while (have_posts()) : the_post(); ?>
!
<h2><a href="<?php the_permalink() ?>" title="<?php the_title();
?>" rel="bookmark"><?php the_title(); ?></a></h2>
<?php echo '<div class="featured-thumbnail">';
the_post_thumbnail(); echo '</div>'; ?>
<div class="post-content">
<?php the_content(__('Read more'));?>
</div>
<?php get_template_part('partials/post-meta'); ?>
<?php endwhile; else: ?>
!
<div class="no-results">
<p>We're sorry, no results were found.</p>
</div><!—noResults-->
!
<?php endif; ?>

Coding Standards
WordPress PHP Coding Standards 
https://make.wordpress.org/core/
handbook/coding-standards/php/
!
PHP The Right Way
http://www.phptherightway.com/

The Basics
from the perspective of the  
world’s smallest theme

style.css index.php
A theme only needs two ﬁles

/*
Theme Name: Smallest Theme
*/
style.css

<!DOCTYPE html>
<html>
<head>
<title>Smallest Theme</title>
</head>
<body>
<h1>Smallest Theme</h1>
</body>
</html>
index.php

<!DOCTYPE html>
<html>
<head>
</head>
<body>
<h1><?php echo 'Smallest Theme in PHP'; ?></h1>
</body>
</html>
index.php

GOTCHAS
PHP statements are like sentences.
Don’t forget the ‘;’ at the end.

Variables
Boolean (true or false)
Integer (numbers)
String (text)
Array (a group of data)
Other types (functions, objects)

<?php
// Boolean - a true or false variable
$wordcamp_is_awesome = true;
!
// Integer - number
$number_of_wordcamps = 4;
!
// String - text
$warm_greetings = 'Thank you for coming to my session!';
?>
!
<!DOCTYPE html>
<html> . . .
index.php

Arrays
Pairs of data with keys and values
Unassigned keys are automatically
given a number value.

<?php
!
// Array - a group of data in key/value pairs
$array_with_keys = array(
'lunch' => 'yummy',
'sessions' => 'awesome',
'after_party' => "Can't wait!"
);
!
$array_wtihout_keys = array(
'yummy', // 0
'awesome', // 1
"Can't wait!" // 2
);
?>
index.php

Data interaction
!
Print to page
‘echo’

<!DOCTYPE html>
<html>
<head>
</head>
<body>
<h1><?php echo 'Smallest Theme in PHP'; ?></h1>
<main>
<p>Welcome to WordCamp Nashville #<?php echo
$number_of_wordcamps; ?></p>
<p>Lunch was <?php echo $array_with_keys[ ‘lunch’ ]; ?>.</p>
</main>
</body>
</html>
index.php

GOTCHAS
You can’t “print” an array without a
loop, but you can print single data
points.

<?php print_r( $array_without_keys ); ?>
!
// Array ( [0] => yummy [1] => awesome [2] => Can't wait! )
!
<?php echo $array_without_keys[ 1 ]; ?>
!
// awesome

Data interaction
!
Return
for use in evaluation

<?php
if ( $wordcamp_is_awesome ) {
$awesomeness = $array_with_keys[ ‘sessions’ ];
} else {
$awesomeness = "Got ya! It's still awesome";
}
?>
<h3>WordCamp is ... <?php echo $awesomeness; ?>!</h3>
index.php

Conditionals
!
test if whatever is in parentheses 
is true

<?php
$awesomeness = $test_array['sessions'];
} else {
}
?>
!
// WordCamp is ...
index.php

<?php
$awesomeness = $test_array[ ‘sessions' ];
} else {
}
?>
!
// WordCamp is ... awesome!
index.php

GOTCHAS
Always surround your conditional with
parentheses.
Don’t forget your curly braces!

Comparison Operators
!
== - Equal To
>,< - Greater/Less Than
>=,<= - Greater/Less Than
or Equal To
!= - Not Equal To

<?php
// Evaluate using a comparison operator
if ( $number_of_wordcamps == 4 ) {
echo '<p>This fourth WordCamp is the best.</p>';
}
?>
index.php

GOTCHAS
= assigns a value to a variable,  
but == evaluates as “is equal to”

Logical Operators
!
&& - And
|| - Or 
! - Not

<?php
// Evaluate using a logical operator
if ( $number_of_wordcamps == 4 && $wordcamp_is_awesome ) {
echo "<p>Now you're getting the hang of it.</p>";
}
?>
index.php

Data interaction
!
Return
for use in built-in WordPress functions

The Loop
!
A conditional statement that  
collects post information

<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
!
. . .
!
<?php endwhile; endif;?>
index.php

<h1><?php the_title(); ?></h1>
!
<?php the_content(); ?>
index.php

Get vs. The
!
When “the” starts a WordPress function
name, it prints directly to the page. 
When “get” starts a WordPress function
name, it simply returns that value to a
variable

<h1><?php the_title(); ?></h1>
!
<h1><?php echo get_the_title( 1 ); ?></h1>
index.php

<footer><?php echo $warm_greetings; ?></footer>
!
// Thank you for coming to my session!
Thank You!

https://github.com/sprclldr/entry-level-php
!
http://www.slideshare.net/sprclldr/entry-
level-php-for-wordpress

@sprclldr
!
kenneth@sprclldr.com
@stellarcowboy

Entry-level PHP for WordPress

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