PHP Data Types

What data types are in PHP

Every value in PHP belongs to a type, and that type controls how the value behaves in comparisons, arithmetic, and function calls. PHP is a dynamically typed language, which means you never declare the type of a variable up front. Instead, the type is decided at runtime by whatever value you assign, and it can change the moment you assign a different value. This flexibility is convenient, but it also means you should stay aware of what type a variable actually holds at any given point.

• String — a sequence of characters, such as "hello".
• Integer — a whole number without a decimal point, such as 42 or -7.
• Float — a number with a decimal point, such as 3.14 (also called double).
• Boolean — one of two logical values, true or false.
• Array — an ordered map that can hold many values under one variable.
• Object — an instance of a class, bundling data and behaviour together.
• NULL — a special type whose only value is null, meaning 'no value'.
• Resource — a reference to an external resource such as an open file or database link.

<?php
$name = "Ada";      // string
$age = 36;           // integer
$height = 1.68;      // float
$isMember = true;    // boolean
$scores = [90, 85, 78]; // array
$note = null;        // NULL

echo $name . " is " . $age . " years old.";
?>

Checking a value's type

Because types are decided at runtime, PHP gives you tools to inspect them. The var_dump() function prints both the type and the value, which makes it ideal for debugging. The gettype() function returns the type name as a string, and there is a family of is_* functions such as is_int(), is_string(), and is_array() that return a boolean so you can branch on the result.

<?php
$price = 19.99;
$quantity = 3;

var_dump($price);        // float(19.99)
var_dump($quantity);     // int(3)

if (is_float($price)) {
    echo "Price is a float";
}
?>

Type juggling and conversion

PHP will often convert a value from one type to another automatically, a behaviour known as type juggling. For example, the numeric string "10" becomes the integer 10 when used in arithmetic. You can also force a conversion yourself with a cast, writing the target type in parentheses before the value, such as (int) or (string). Explicit casts make your intent clear and help avoid surprises.

<?php
$result = "10" + 5;      // string juggled to int, result is 15
echo $result;            // 15

$number = (int) "42abc"; // explicit cast, result is 42
echo $number;            // 42

$text = (string) 3.5;    // explicit cast to string
var_dump($text);         // string(3) "3.5"
?>