JuniorTheoryCommon

What does the program print?

PHP

<?php

interface Shape
{
    public function area(): float;
}
class Square implements Shape
{
    public function area(): float { return 3 ** 2; }
}
$s = new Square();
echo $s instanceof Shape ? 'yes' : 'no', ' ', $s->area(), "\n";

yes 9

Expecting instanceof to check only the object's own class: it is true for the class, each of its parents and each interface it implements, so $s instanceof Shape is true.
Expecting echo to print 9.0 for a float result: echo drops a zero fractional part, so 9.0 prints as 9; var_dump shows the type.

What does instanceof return when its left side is not an object?
What happens if Square declares implements Shape but has no area() method?

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JuniorTheoryCommon

What does the program print?

PHP

<?php

interface Shape
{
    public function area(): float;
}
class Square implements Shape
{
    public function area(): float { return 3 ** 2; }
}
$s = new Square();
echo $s instanceof Shape ? 'yes' : 'no', ' ', $s->area(), "\n";

yes 9

Expecting instanceof to check only the object's own class: it is true for the class, each of its parents and each interface it implements, so $s instanceof Shape is true.
Expecting echo to print 9.0 for a float result: echo drops a zero fractional part, so 9.0 prints as 9; var_dump shows the type.

What does instanceof return when its left side is not an object?
What happens if Square declares implements Shape but has no area() method?

Back to questions Open topic in roadmap →Answer it yourself — Quiz