How to replace "if" statement with a ternary operator ( ? : )?

Question

The

(condition) ? /* value to return if condition is true */ 
            : /* value to return if condition is false */ ;

syntax is not a "shorthand if" operator (the ? is called the conditional operator) because you cannot execute code in the same manner as if you did:

if (condition) {
    /* condition is true, do something like echo */
}
else {
    /* condition is false, do something else */
}

In your example, you are executing the echo statement when the $address is not empty. You can't do this the same way with the conditional operator. What you can do however, is echo the result of the conditional operator:

echo empty($address['street2']) ? "Street2 is empty!" : $address['street2'];

and this will display "Street is empty!" if it is empty, otherwise it will display the street2 address.

PHP 7+

As of PHP 7, this task can be performed simply by using the Null coalescing operator like this :

echo $address['street2'] ?? 'Empty';

Basic True / False Declaration

$is_admin = ($user['permissions'] == 'admin' ? true : false);

Conditional Welcome Message

echo 'Welcome '.($user['is_logged_in'] ? $user['first_name'] : 'Guest').'!';

Conditional Items Message

echo 'Your cart contains '.$num_items.' item'.($num_items != 1 ? 's' : '').'.';

ref: https://davidwalsh.name/php-ternary-examples

It's the Ternary operator a.k.a Elvis operator (google it :P) you are looking for.

echo $address['street2'] ?: 'Empty'; 

It returns the value of the variable or default if the variable is empty.

The ternary operator is just a shorthand for and if/else block. Your working code does not have an else condition, so is not suitable for this.

The following example will work:

echo empty($address['street2']) ? 'empty' : 'not empty';

Quick and short way:

echo $address['street2'] ? : "No";

Here are some interesting examples, with one or more varied conditions.

$color = "blue";

// Example #1 Show color without specifying variable 
echo $color ? : "Undefined";
echo "<br>";

// Example #2
echo $color ? $color : "Undefined";
echo "<br>";

// Example #3
echo ($color) ? $color : "Undefined";
echo "<br>";

// Example #4
echo ($color == "blue") ? $color : "Undefined";
echo "<br>";

// Example #5
echo ($color == "" ? $color : ($color == "blue" ? $color : "Undefined"));
echo "<br>";

// Example #6
echo ($color == "blue" ? $color : ($color == "" ? $color : ($color == "" ? $color : "Undefined")));
echo "<br>";

// Example #7
echo ($color != "") ? ($color != "" ? ($color == "blue" ? $color : "Undefined") : "Undefined") : "Undefined";
echo "<br>";