Type Casting

As we know, PHP is more than capable of assigning data types to our variables based on the value assigned to the variable. However, if we update a variable to a value with a different data type, the data type gets altered. Take the following:

$age = "42";
echo gettype($age); // Output: string
 
$age = 42;
echo gettype($age); // Output: integer

The $age variable goes from a string to an integer. But we're taking the extra step to update the variable just to change its data type. It's not uncommon to have to change the data type at a moment's notice. PHP supports typecasting to make this process easy.

What is typecasting?

Type casting in PHP is the process of converting a value from one data type to another in a way that you, the developer, explicitly control. In other words, type casting gives you more control over the data types of your values.

For example, if you have a string value "10" and you want to perform arithmetic operations on it, you can explicitly convert it to an integer using type casting, like this:

(int) "10";

The name of the data type must be written before the value wrapped with parentheses. We can use the following type casts:

• cast to an integer by using (int) or (integer)
• cast to boolean using (bool) or (boolean)
• cast to float using (float) or (double)
• cast to string using (string)

Type casting integers

There are a few things to keep in mind when casting non integers into an integer:

• Casting a boolean false converts into 0. Likewise, casting a boolean true convert into 1.
• Casting float numbers will cause the PHP interpreter to round the decimal values toward zero.
• If a string is fully numeric, it'll be converted into the correct integer. However, strings with non-numeric characters will be converted into 0.
• null is converted into 0.

Here are some examples:

Here are some code examples:

echo (int) false;       // Output: 0
echo (int) true;        // Output: 1
echo (int) "-1";        // Output: -1
echo (int) "null";      // Output: 0
echo (int) "Hello";     // Output: 0
echo (int) "12 months"; // Output: 12
echo (int) 1.2e8;       // Output: 120000000
echo (int) 14.7;        // Output: 14
echo (int) -5.9;        // Output: -5

Type casting floats

There are a few things to keep in mind when casting non-floats into an float:

• Strings containing numbers will be transformed into the same numeric value. Anything else is transformed into 0.
• PHP transforms any other data types into an integer, which is then transformed into a float. Here are some examples:

Here are some code examples:

echo (float) false;           // Output: 0
echo (float) true;            // Output: 1
echo (float) "-1";            // Output: -1
echo (float) "null";          // Output: 0
echo (float) "Hello";         // Output: 0
echo (float) "12.24 months";  // Output: 12.24
echo (float) 1.2e8;           // Output: 120000000

Type casting booleans

There are only two possible values that can be generated when type casting to a boolean, which are true and false. PHP transforms a value into false based on the following conditions:

• When the integer value is 0
• When the float value is 0.0
• Empty strings
• The string "0"
• When the value is null

Here are some code examples:

echo (bool) "false";  // Output: 1
echo (bool) 0;        // Output:
echo (bool) "0";      // Output:
echo (bool) "zero";   // Output: 1
echo (bool) "";       // Output:
echo (bool) -1;       // Output: 1

Type casting strings

There are a few things to keep in mind when casting non-strings into a string:

• A false boolean value becomes an empty string, and a true value becomes the string "1".
• Integers and floats are converted to a textual representation of those numbers.
• The value NULL is always converted to an empty string.

Here are some code examples:

echo (string) false;    // Output:
echo (string) true;     // Output: 1
echo (string) 0;        // Output: 0
echo (string) 1.4545;   // Output: 1.4545
echo (string) -5;       // Output: -5
echo (string) null;     // Output:

Exercise

Try type casting the following values:

• The string "Hello world" into a boolean.
• The boolean true into an integer.
• The integer 55 into a float.
• The float 54.55 into a string.

Key takeaways

• Type casting is the process of changing the data type of a value from one type to another.
• Developers can perform typecasting by specifying the type before the value wrapped with parentheses i.e. (bool).