In PHP, variables can store all sorts of data — strings, numbers, booleans, arrays, and so on. Each type behaves a little differently, but PHP handles most of this automatically. That’s part of what makes it so flexible.

You can always check what kind of data a variable holds with var_dump().

$x = 5;
var_dump($x);

That’ll tell you both the type and the value.

A string is just text — something wrapped in quotes. Both single and double quotes work:

$name = "Pretty Links";
$tagline = 'Track and manage your URLs easily.';
var_dump($name);
var_dump($tagline);

The difference between single and double quotes, as we’ve seen before, is that double quotes can interpret variables inside them.

An integer is a whole number — no decimals, just straight values like 42 or -300.

$activeMembers = 5985;
var_dump($activeMembers);

A float (or “double”) is a number that includes decimals, like when you’re working with prices or measurements.

$conversionRate = 10.365;
var_dump($conversionRate);

A boolean is either true or false. They’re often used for simple logic, like checking if a MemberPress subscription is active or not:

$isActive = true;
var_dump($isActive);

An array is a way to store multiple values under one variable — like a list of supported plugins in the CaseProof ecosystem:

$plugins = ["MemberPress", "Pretty Links", "ThirstyAffiliates"];
var_dump($plugins);

Then there are objects, which come from classes. Think of a class as a “blueprint” — and each object as something built from that blueprint. If you had a class representing a plugin, each instance might represent a specific one with its own properties.

class Plugin {
  public $name;
  public $type;

  public function __construct($name, $type) {
    $this->name = $name;
    $this->type = $type;
  }

  public function describe() {
    return "This is a {$this->type} plugin called {$this->name}.";
  }
}

$mp = new Plugin("MemberPress", "membership");
var_dump($mp);

Don’t worry too much about objects yet — there’s a whole section on that later.

NULL is PHP’s way of saying “nothing here.” It’s a special data type that literally means the variable has no value.

$discount = null;
var_dump($discount);

If you create a variable but don’t assign anything, PHP automatically gives it NULL by default.

Now, PHP is smart enough to change a variable’s type based on what you assign to it:

$x = 5;
var_dump($x);

$x = "Five";
var_dump($x);

If you do want to manually change a variable’s type without changing its value, you can cast it:

$x = 5;
$x = (string) $x;
var_dump($x);

Finally, there’s resource, which isn’t a “real” data type in the usual sense — it represents a reference to something external, like a database connection or a file handle. You’ll see that in action when working with databases or API calls.