Wordpress & PHP Resources

Background

I started this markdown file as a place to collect information about Wordpress and PHP when I started programming a Wordpress plugin for the first time. I decided to put out everything I could find in this gist. I will update it occassionally with code examples so I can track my progress in developing Wordpress plugins (or just the one I'm working on at work).

Wordpress 101

Wordpress Environment

For OSX: MAMP
Wordpress.org
For FTP: FileZilla

Learning Wordpress

Team Treehouse Wordpress Videos

Wordpress Plugins

Wordpress Plugin Resources

Connecting to APIs

Wordpress.org Codex: WP_Remote_GET

Hooks

WP Hooks === Conditionals where you can insert some function (actions and filters). Adam Brown has a list of hooks you can develop on top of.

Wordpress Admin Styles
Action Hooks: Run your own code when an event occurs
Filter Hooks: Modify existing code within Wordpress

Wordpress Template Tags

Wordpress.org Codex: Template Tags

Loops (i.e. WP_Query)

WP_Query

Wordpress Coding Standards

Wordpress Debugging

Wordpress.org Codex: WP_DEBUG

Dev Project Management

Composer with Wordpress

PHP Programming

PHP Types

Four scalar types:

Integer type PHP Docs
Float type PHP Docs
String type PHP Docs
Boolean type PHP Docs

Two compound types:

Array Type PHP Docs
Object Type PHP Docs

And finally two special types:

Resource Type PHP Docs
NULL Type PHP Docs

Constants are ALL_CAPS and do not start with a '$'.

<?php
    define('YEAR', 2014);
    define('JOB_TITLE', 'Teacher');
?>

Arrays can be initiated two ways.

<?php
    $array_example = array(); // or
    $array_example = [];

    // adding to array (like push() in JS)
    $array_example[] = 'Amber';
?>

Associative arrays are like hashes in Ruby or dictionaries in Python.

<?php
    $another_array = array(
        'chris' => 'blue',
        'tom' => 'green',
        'jim' => 'brown'
    );

    echo $another_array['chris']; // returns 'blue'
?>

gettype() - Returns type of the variable. PHP Docs
Strings are 0 based index

<?php
    $variable = "Hello World."
    echo $variable{0} // "H"
?>

PHP Operators

Concatenation uses the . symbol.

<?php
    $assignment = "hello" . "world";
    echo $assignment // "hello world"
?>

Casting, or typecasting, can allow you to assign a type to your variable.

<?php
    $variable_one = 1;
    $variable_two = (string) $variable_one;
    echo $variable_two // "1" as a string
?>

PHP Conditional syntax:

isset() - Returns true of false depending if variable is set. PHP Docs

<?php
    if (/* conditional */) {
        // do something
    } elseif (/* another conditional */) {
        // do something
    } else {
        // do something else
    }
?>

PHP Looping

For loop example.

<ul>
<?php
    for($counter=0; $counter < 2; $counter++) {
        echo "<li>" . $counter . "<li>";
    }
?>
</ul>

ForEach loop example.

<?php

    forEach($social_icons as $icon) {
    ?>
        <li><a href=""><span class="icon <?php echo $icon ?>"></a></li>
    <?php
    }
?>

PHP function

Function scope is isolated within its block. If we're going to use a global variable (or outside of the function scope), it must be added into the function scope with a global statement.

<?php
    $current_user = 'Jeremy';
    function hello() {
        global $current_user; // Without this statement, $current_user can not be used within the function scope
        // do something
    }
?>

Arguments can be passed by reference. This means if you want to change the argument variable outside the function scope, you need to add an & in front of the argument. By default, arguments are passed as values.

<?php
    function add_some_extra(&$string)
    {
        $string .= 'and something extra.';
    }
    $str = 'This is a string, ';
    add_some_extra($str);
    echo $str;    // outputs 'This is a string, and something extra.'
?>

Default arguments can also be passed.

<?php
    function hello($name = 'friend') {
        echo 'Hi, $name';
    }
    hello(); // by default, 'Hi, friend'
?>

Returns are not implicit. If no return is passed, NULL will be passed back.

Variable Functions - calling variables given a string variable value. Very valuable for callbacks.

<?php
    function add_up($1, $b) {
        return $a + $b;
    }

    $func = 'add_up';

    $num = $func(5, 10);

    echo $num; // 15
?>

Closures are anonymous functions, also useful for callbacks. The use keyword is important here.

<?php
    $name = 'friend';
    $greet = function() use ($name) {
        echo 'Hello $name.';
    }

    $greet(); // 'Hello friend.'
?>

Objects

Accessing its properties (the class public variable) within the class, you need to use an object operator ->. $this->//Property of class

Visibility:

public
private
protected - Members declared protected can be accessed only within the class itself and by inherited and parent classes.

Constructors:

<?php
class Person {
    public $name;

    function __construct($args) {
        $this->name = $args['name'];
    }

    public function showName() {
        echo $this->name;
    }
}

$carrot_top = new Person(array(
    'name' => 'Carrot Top'
));

$carrot_top->showName(); // 'Carrot Top'
?>

Classes

Arrow or Chevron vs. double colon (-> vs. ::) explained

It turns out, you use the -> for dynamic methods while you use :: for static method. Usually explicit in the function name. public static function.

Built-in Functions

Strings

strlen String Length
substr Substring
strpos String position. Returns bool(false) if string passed is not found.

Printing in PHP

echo - Output one or more strings
print_r - Prints array
printf - Output a formatted string
fprintf - Write a formatted string to a stream
sprintf - Return a formatted string
print_r - Variable handling function - Prints human-readable information about a variable
var_dump - Variable handling function - Returns information about a variable. PHP Docs

Arrays

array_keys Returns all the keys or a subset of keys of an array
array_walk Callback applied to elements in a given array

Error Handling

With APIs, there is no try/catch for cUrl since it's based on the C Library. StackOverflow

<?php
$options[CURLOPT_URL] = 'https://[domain]/test.htm';

$options[CURLOPT_PORT] = 443;
$options[CURLOPT_FRESH_CONNECT] = true;
$options[CURLOPT_FOLLOWLOCATION] = false;
$options[CURLOPT_FAILONERROR] = true;
$options[CURLOPT_RETURNTRANSFER] = true; // curl_exec will not return true if you use this, it will instead return the request body
$options[CURLOPT_TIMEOUT] = 10;

// Preset $response var to false and output
$fb = "";
$response = false;// don't quote booleans
echo '<p class="response1">'.$response.'</p>';

$curl = curl_init();
curl_setopt_array($curl, $options);
// If curl request returns a value, I set it to the var here. 
// If the file isn't found (server offline), the try/catch fails and var should stay as false.
$fb = curl_exec($curl);
curl_close($curl);

if($fb !== false) {
    echo '<p class="response2">'.$fb.'</p>';
    $response = $fb;
}

// If cURL was successful, $response should now be true, otherwise it will have stayed false.
echo '<p class="response3">'.$response.'</p>';

jermspeaks/wordpress.md