Learn PHP:11-Data Types and PHP Automatic Data Typing

Posted: November 3, 2010 in PHP

PHP sports a cool feature called automatic data typing. A PHP developer can claim variables and use them in most common situations without having to claim the data type that the variable is. But this is also a double edged sword because as a developer gets more advanced they may create functions or scripts that only accept one data type, and throw errors if you feed it a different type. But that is usually only in the most complex of PHP applications.

For instance, if my imported script and function is expecting an integer type variable and I feed it a string type, I will get an error and know that I must not try to feed it a string… it needs an integer type variable. No big deal, I will just make sure a number type variable is all that gets sent through that mechanism.

Here are the data types:
Boolean, Integer, Floating Point Number, String, Array, Object, Resource, Null

// Boolean... true or false data types
$userChoice = true;

// Integer.... whole numbers
$num1 = 3;

// Floating Point Numbers
$num2 = 8.357

// String... a set of alphanumeric characters
$string1 = "Hello World, I just turned 21!";

// Array... we cover building arrays in later lessons
$my_friend_array = array(1 => 'Joe', 2 => 'Adam', 3 => 'Brian', 4 => 'Susan', 5 => 'Amy', 6 => '0', 7 => 'Bob');

// Object...
// Objects work with classes, which we will cover later

// Resource...
// A special variable, holding a reference to an external resource.
// Resources are created and used by special functions.

// Null... value for missing, empty, or unset variables. If null... it has no value and is not set.
$var1 = NULL; // Casting a variable to null will remove the variable and unset its value

PHP has functions to test whether or not a variable is a certain “type”. This is known as the is_* function family.

// set the variable and its value
$myVar = "Adam Khoury";
// Run simple if and else statement to see if it is a string or not
if (is_string($myVar)) {
echo "Yes";
} else {
echo "No";


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