PHP Data Types

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In this tutorial we will learn about PHP data types.

Data types

PHP supports 8 data types. A variable's data type tells us about the type of operations that can be performed on the data and the memory space the value of that data type will occupy.

Following are the list of 4 simple data type. They can hold only one value at a time.

Data Type Description Example
Boolean A data type that can have only two values either true or false. $is_game_over = true;
Integer This represents set of integer numbers both positive and negative. $count = 10;
Float This represents set of numbers both positive and negative and with fractional part. $g = 9.8;
String This represents a series of characters enclosed within double quotes. Single quotes can also be used. $name = "Yusuf Shakeel";
$country_name = 'India';

Following are the list of 2 compound data type. These are the data type that can hold multiple values.

Data Type Description
Array Array variables are basically an ordered map.
Object It is a data type that consists of properties and methods.

We will talk about array and object in detail in their respective tutorial.

Following are the list of 2 special data type.

Data Type Description
Null This can take only one value null and if a variable is set to null then it means that the variable explicitly does not contain any value.
Resource It contains a reference to an external resource like file or database connection.

PHP is loosely typed

Now this is a very important point to note. PHP is loosely typed means that PHP does not care what value you store in a variable as the data type is automatically determined based on the context in which the variable is used.

For example

$x = 10;

In the above line we have created a variable $x and it is assigned an integer value 10. So, the data type of variable $x is Integer. Now we will do a very interesting thing.

$x = "Sunday";

We have now set a string value to the same variable $x. This time, the data type of variable $x is String.

The interesting thing is we can assign any type of value to a variable and the data type of that variable will be determined as per the current value it is holding.

This is completely different from strongly typed languages like Java and C++ where we cannot assign a string value to an integer variable as they are of different data type.

Note! The loosely typed nature of PHP can easily become a cause of error. So, take extra care while assigning value to variables.

Determine data type of a variable

We can use the function gettype() to determine the data type of a variable. Lets check few example.

$name = "Yusuf Shakeel";
echo gettype($name);

This will print "string" as $name contains a String data.

$age;
echo gettype($age);

This will print "null" as we have created a variable $age but it is not initialized with any value so it contains null.

We can also use the following functions to determine the data type of the variable.

Function Result
is_bool($var) If $var is of type Boolean then return true, otherwise false
is_int($var) If $var is of type Integer then return true, otherwise false
is_float($var) If $var is of type Float then return true, otherwise false
is_string($var) If $var is of type String then return true, otherwise false
is_array($var) If $var is of type Array then return true, otherwise false
is_object($var) If $var is of type Object then return true, otherwise false
is_resource($var) If $var is of type Resource then return true, otherwise false
is_null($var) If $var is of type Null then return true, otherwise false

Changing data type of a variable using settype()

We can change the data type of a variable using the settype() function. This function takes two parameters. The first one is for the variable and the second is for the type.

In the following example we are changing the data type of integer variable $x to string.

$x = 10;	//this is an integer variable

settype( $x, "string" );	//setting type of $x to string

echo gettype($x);	//this will print "string"

Changing data type of a variable's value using type casting

We can use type casting to change the variable's value to a specific type. In this method we are only targeting the value of the variable so the data type of the variable will remain unchanged.

$weight = 100.20;	//data type float (double)

echo gettype($weight);	//double

//now we will type cast the value of $weight to integer

echo (int) $weight;		//100   double value is changed to integer so fractional part is truncated.

echo gettype( (int) $weight );	//integer  this is the type of the value

echo gettype($weight);	//double

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