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;