php language basics

Types And Values

Every value in PHP has a type. The type tells PHP what kind of value it is working with and which operations make sense.

Start with four common values from a product record:

PHP example

<?php

$productName = 'Notebook';
$priceCents = 1299;
$inStock = true;
$discount = null;

var_dump($productName);
var_dump($priceCents);
var_dump($inStock);
var_dump($discount);

// Prints:
// string(8) "Notebook"
// int(1299)
// bool(true)
// NULL

var_dump() shows the type and the value. It is useful while learning and while debugging.

Common Types

string: text such as a product name.
int: whole numbers such as a quantity or price in cents.
float: numbers with a fractional part.
bool: either true or false.
null: an intentionally missing value.
array: a group of values.

PHP example

<?php

$tags = ['php', 'beginner'];
$rating = 4.5;

var_dump($tags);
var_dump($rating);

// Prints:
// array(2) {
//   [0]=>
//   string(3) "php"
//   [1]=>
//   string(8) "beginner"
// }
// float(4.5)

Objects, resources, and callables are introduced later. For now, learn to recognise the type you have before trying to use it.

Values From Outside PHP Need Care

A submitted form field normally arrives as text, even when it looks like a number. The string '10' and the integer 10 are related but not identical values.

PHP example

<?php

var_dump('10');
var_dump(10);

// Prints:
// string(2) "10"
// int(10)

Later lessons cover comparisons and validation. The important habit is to inspect and understand incoming values instead of assuming their type.

Practice

Inspect Product Values

Create values for a product name, price in cents, stock status, and missing discount. Use var_dump() to inspect each one.

Show solution

PHP example

<?php

$name = 'Notebook';
$priceCents = 1299;
$inStock = true;
$discount = null;

var_dump($name, $priceCents, $inStock, $discount);

// Prints:
// string(8) "Notebook"
// int(1299)
// bool(true)
// NULL

Predict Two Types

Predict the var_dump() output for '25' and 25, then run the script. Explain the difference.

Show solution

PHP example

<?php

var_dump('25');
var_dump(25);

// Prints:
// string(2) "25"
// int(25)

The quoted value is text. The unquoted whole number is an integer.

Build A Typed Summary

Create an array containing a product name, integer quantity, float rating, boolean stock flag, and null discount. Inspect the array with var_dump().

Show solution

PHP example

<?php

$product = [
    'name' => 'Notebook',
    'quantity' => 3,
    'rating' => 4.5,
    'in_stock' => true,
    'discount' => null,
];

var_dump($product);

The dump shows that one array can contain values with different types. Later lessons cover how to read those keys safely.