Home and Learn: PHP Programming Course
A Boolean value is one that is in either of two states. They are known as True or False values, in programming. True is usually given a value of 1, and False is given a value of zero. You set them up just like other variables:
$true_value = 1;
$false_value = 0;
You can replace the 1 and 0 with the words "true" and "false" (without the quotes). But a note of caution, if you do. Try this script out, and see what happens:
<?php
$true_value = true;
$false_value = false;
print ("true_value = " . $true_value);
print (" false_value = " . $false_value);
?>
What you should find is that the true_value will print "1", but the false_value won't print anything! Now replace true with 1 and false with 0, in the script above, and see what prints out.
Boolean values are very common in programming, and you often see this type of coding:
$true_value = true;
if ($true_value) {
print("that's true");
}
This is a shorthand way of saying "if $true_value holds a Boolean value of 1 then the statement is true". This is the same as:
if ($true_value == 1) {
print("that's true");
}
The NOT operand is also used a lot with this kind of if statement:
$true_value = true;
if (!$true_value) {
print("that's true");
}
else {
print("that's not true");
}
You'll probably meet Boolean values a lot, during your programming life. It's worth getting the hang of them!
In recent editions of PHP, two new operators have been introduced: the triple equals sign ( = = =) and an exclamation, double equals ( != =). These are used to test if one value has the same as another AND are of the same type. An example would be:
$number = 3;
$text = 'three';
if ($number === $text) {
print("Same");
}
else {
print("Not the same");
}
So this asks, "Do the variables match exactly?" Since one is text
and the other is a number, the answer is "no", or false. We won't
be using these operators much, if at all!
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