[PHP4WP#1] PHP for WordPress – Linkedin Course

Notes:

• Introduction
  • Other course
    • WordPress 5 Essential Training
    • Become a web developer (Learning Path)
• PHP BASICS
  • PHP Hypertext Programming language.
  • Key areas
    • Input and output
    • Variables
    • Controlling flow in your code
    • Arrays
    • Generalizing with functions
  • Code block

<?php
   // PHP code lines go here
?>

<?php echo "Hello World"; ?> //one statemends ends with semicolon

• …
  • PHP coding conventions
    • All PHP files must end in .php
    • Statements (or commands) in PHP end with a semicolon (;)
    • If you want to include comments, which are nonfunctional notes, you can do so in two ways

//Single-line comments are two forward slashes.

/* Multiline, or block comments, start with a
forward slash and an asterisk. They end with an asterisk
and forward slash. */

• …
  • Variables
    • A way to store information in order to reference it later

<?php
$age = 34;
echo $age;

$age = 35;

$double_age = $age * 2;
echo $double_age;//Outputs 70
?>

<?php
  $username= get_logged_in_user();
  echo "Hello $username!";
?>

Variable types

• PHP a weak-typed language, where PHP takes care of what kind of data we store in a variable.
• Types of variable
  • Integers, whole numbers
  • Floats, numbers with decimals
  • Characters, single letters, numbers, or symbols
  • Strings
  • Booleans
  • Arrays
• 1 vs ‘v’
  • You can do calculation with 1 but not ‘1’

STRINGS IN PHP

• Double Quotes
  • Strings in double quotes will be processed by PHP before they’re outputted.

<?php 
  $age = 34;
  echo "Joe is $age years old";//Joe is 34 years old
  echo 'Joe is $age years old'; //Joe is $age years old
  echo 'Joe is '.$age.' years old.'; //Joe is 34 years old

?>

In below example not the single quote inside double quote and escaping characters.

<?php 
  $age = 34;
  echo "Joe's nickname in high school was \"Joey colzone\"";//Joe's nickname in high school was "Joey colzone"


?>

• Escaping characters (only used with double quotes or sometimes with single quote)
  • \n for a new line
  • \\ for a backslash
  • \$ for a dollar sign
  • \t for a tab

<?php 
  $age = 34;
  echo "Joe is $age years old\n";//Joe is 34 years old
  echo "This is the second line\n";
  echo 'Joe\'s nickname is J';//Joe's nickname is J

?>

USING ARRAYS

<?php 
  $colors =array('red','green','blue','yellow');
  print_r( $colors);
?>

output of above code

Array
(
    [0] => red
    [1] => green
    [2] => blue
    [3] => yellow
)

printing out single element of arrays

<?php 
  $colors =array('red','green','blue','yellow');
  echo $colors[1];//green
?>

We can also use string indexes

<?php 
  $colors =array('red','green','blue','yellow');
  
  $joe = array(
    'name' => 'Joe Casabona',
    'page' => 34,
    'job'  => 'Freelancer',
  );

  print_r($joe);
  echo $joe['job'];//Freelancer
?>

output

Array
(
    [name] => Joe Casabona
    [page] => 34
    [job] => Freelancer
)
Freelancer

Multi-dimensional arrays

<?php 
  $colors =array('red','green','blue','yellow');
  
  $family_members = array(
    'papa' => array(
      'name' => 'Rakesh Mehta',
      'age' => 55,
    ),
    'mom' => array(
      'name' => 'Seema Mehta',
      'age' => 49,
    ),
    'me' => array(
      'name' => 'Dikshant Mehta',
      'age' => 25,
    ),
    'sis' => array(
      'name' => 'Garima Mehta',
      'age' => 23,
    ),
  );

  print_r( $family_members);
  echo $family_members['papa']['name']."\n";//Rakesh Mehta
  print_r( $family_members['papa']); // output array of papa
?>

output

Array
(
    [papa] => Array
        (
            [name] => Rakesh Mehta
            [age] => 55
        )

    [mom] => Array
        (
            [name] => Seema Mehta
            [age] => 49
        )

    [me] => Array
        (
            [name] => Dikshant Mehta
            [age] => 25
        )

    [sis] => Array
        (
            [name] => Garima Mehta
            [age] => 23
        )

)
Rakesh Mehta
Array
(
    [name] => Rakesh Mehta
    [age] => 55
)

Arithmetic operators and math in PHP

Arithmetic operators

• Addition +
• Subtraction –
• Multiplication with *
• Division with /
• Get the remainder with %

PHP is smart to evaluate the variable or the literal operation.

echo 1+1; //2

echo 14 % 8;//will print out 6

PEMDAS – order of mathematical operations

1. Parentheses
2. Exponents
3. Multiplication and Division
4. Addition and Subtraction

echo 3**2;//Print out exponent result 9

Challenge: Perform a mathematic operation and store it

<?php
 $results = array();
 $results[] = 9 + 2 *5 - 11;
 $results[] = 18 / (3 * 6 - 9) * 3;
 $results[] = 3 * (24 / 2 - 3 * 4 + 2 * 6);

 print_r( $results );

?>

output

Array
(
    [0] => 8
    [1] => 6
    [2] => 36
)

We use array for coding convenience and to speed up operations.