PHP Data Types

Every value in PHP has a type. The type decides what you can do with the value. You can add two numbers, but adding two names makes no sense.

PHP has these main types:

Looking at a value: var_dump()

var_dump() prints the type and the value. It is the most useful debugging tool for a beginner.

1
2
3
4
5
6

<?php
var_dump("Hello");
var_dump(42);
var_dump(3.14);
var_dump(true);
var_dump(null);

1
2
3
4
5

string(5) "Hello"
int(42)
float(3.14)
bool(true)
NULL

string(5) means a string with 5 characters.

Just the type name: gettype()

1
2
3
4
5

<?php
echo gettype("Hello") . "\n";
echo gettype(42) . "\n";
echo gettype(3.14) . "\n";
echo gettype([1, 2]) . "\n";

1
2
3
4

string
integer
double
array

gettype() has old names (“integer”, “double”). A newer function, get_debug_type(), uses the names you write in code (int, float).

1
2
3
4

<?php
echo get_debug_type(42) . "\n";
echo get_debug_type(3.14) . "\n";
echo get_debug_type(null);

1
2
3

int
float
null

Variables do not have types, values do

A PHP variable can hold any type, and it can change.

1
2
3
4
5
6

<?php
$data = 5;
var_dump($data);

$data = "five";
var_dump($data);

1
2

int(5)
string(4) "five"

The next lessons look at each type in turn.