Booleans and Comparison Operators in PHP

PHP else statement

A PHP else statement can follow an if block. If the condition of the if does not evaluate to TRUE, the code block following else will be executed.

$condition = FALSE;
if ($condition) {
  // This code block will not execute
} else {
  // This code block will execute
}

PHP comparison operators

PHP comparison operators are used to compare two values and return TRUE or FALSE depending on the validity of the comparison. Comparison operators include:

identical (===)
not identical (!==)
greater than (>)
less than (<)
greater than or equal (>=)
less than or equal (<=)

// Comparison operators
1 > 3; // FALSE
3 > 1; // TRUE
250 >= 250; // TRUE
1 === 1; // TRUE
1 === 2; // FALSE
1 === "1"; // FALSE

PHP If Statements

PHP if statements evaluate a boolean value or expression and execute the provided code block if the expression evaluates to TRUE.

if (TRUE){
  echo "TRUE is always true"; 
}

$condition1 = TRUE;
if ($condition1) {
  // This code block will execute
}

$condition2 = FALSE;
if ($condition2) {
  // This code block will not execute
}

PHP switch statement

PHP switch statements provide a clear syntax for a series of comparisons in which a value or expression is compared to many possible matches and code blocks are executed based on the matching case.

In PHP, once a matched case is encountered, the code blocks of all subsequent cases (regardless of match) will be executed until a return, break, or the end of the statement is reached. This is known as fall through.

switch ($letter_grade){
  case "A":
    echo "Terrific";
    break;
  case "B":
    echo "Good";
    break;
  case "C":
    echo "Fair";
    break;
  case "D":
    echo "Needs Improvement";
    break;
  case "F":
    echo "See me!";
    break;
  default:
    echo "Invalid grade";
}

PHP readline()

The PHP built-in readline() function takes a string with which to prompt the user. It waits for the user to enter text into the terminal and returns that value as a string.

echo "\nWhat's your name?\n";
$name = readline(">> "); // receives user input

PHP elseif statements

PHP elseif statements must be paired with an if statement, but many elseifs can be chained from a single if.

elseifs provide an additional condition to check (and corresponding code to execute) if the conditional statements of the if block and any preceding elseifs are not met.

$fav_fruit = "orange";

if ($fav_fruit === "banana"){
  echo "Enjoy the banana!";
} elseif ($fav_fruit === "apple"){
  echo "Enjoy the apple!";
} elseif ($fav_fruit === "orange"){
  echo "Enjoy the orange!";
} else {
  echo "Enjoy the fruit!";
}
// Prints: Enjoy the orange!

PHP Truthy and Falsy

PHP values within a condition will always be evaluated to TRUE or FALSE. Values that will evaluate to TRUE are known as truthy and values that evaluate to FALSE are known as falsy.

Falsy values include:

false
0
empty strings
null
undefined
NaN.

All other values are truthy.

if ("What's going on?"){   // evaluates to TRUE
  echo "Let us explain…";
} 
// Prints: Let us explain…

PHP Boolean Values

PHP Boolean values are either TRUE or FALSE, which are the only members of the boolean type

// booleans
$is_true = TRUE;
$is_false = FALSE;

echo gettype($is_true); 
// Prints: boolean
echo gettype($is_false); 
// Prints: boolean

PHP ternary operator

In PHP, the ternary operator allows for a compact syntax in the case of binary (if/else) decisions. It evaluates a single condition and executes one expression and returns its value if the condition is met and the second expression otherwise.

The syntax for the ternary operator looks like the following:

condition ? expression1 : expression2

// Without ternary
$isClicked = FALSE;
if ($isClicked) {
  $link_color = "purple";
} else {
  $link_color = "blue";
}
// $link_color = "blue";


// With ternary
$isClicked = FALSE;
$link_color = $isClicked ? "purple" : "blue";
//  $link_color = "blue";