phpapprentice/chapters/basics/05-comparisons.md

A boolean is a value that is always 0 or 1, yes or no, on or off. In PHP, a boolean is represented by the words true and false. While programming, you will often want to know if something is positive or negative.

<?php

$a = true;
$b = false;

There are many constructs and functions that will return a boolean. To start, let's look at comparisons.

Double equals checks if two values are equal.

$one = 1;
$two = 2;

$one == $two; // returns false

An exclamation point and equal sign check if two values are not equal.

$one != $two; // returns true

You can use greater than and less than symbols to check for comparisons too.

$one > $two; // returns false
$one < $two; // returns true

If you combine a greater than or less than symbol with an equal, it will check if the value is greater or less than or equal to another value.

$one <= $two;
$one >= $two;

You can also check that two values are equal and of the same type by using three equal signs.

The following comparisons return true.

1 == 1;
1 == '1';
1 == true;
1 == 1.0;
1 === 1;

These return false.

1 === '1';
1 === true;
1 === 1.0;