Why is PHP referred to as a loosely typed language?
  John Mwaniki /   16 Sep 2021

Why is PHP referred to as a loosely typed language?

As a new programmer, you have or are likely to come across the phrase "loosely typed language" used to describe some programming languages.

All programming languages can be classified as either strongly or weakly/loosely typed programming languages.

PHP is a widely-used programming language for web development and is often referred to as a loosely typed language.

Javascript is another example of a loosely typed language. Let's dive into understanding what the phrase means.

What is a loosely typed language?

A loosely typed programming language is a language that does not require the data type of a variable to be explicitly defined.

In computer programming, data used are classified into different types referred to as data types.

A data type is a classification of data that specify to the compiler or interpreter which value a variable can take and the operations that can be performed on it.

Examples of data types include integer, float, double, char, string, boolean, array, etc.

In strongly typed languages, computer programmers must explicitly specify the data type when defining variables.

Examples of strongly typed languages include C, Java, C++, Go, Python, etc.

On the other hand, in PHP and other loosely typed programming languages, you can easily create variables without having to worry about which data type they belong to.

You create all variables the same way without defining the data type like in the PHP example below:

$myinteger = 25;
$mystring = "Hello World!";
$mybool = true;

In PHP, all you have to do is start with a dollar sign ($) followed by the variable name and you can assign to it, data of any type.

A loosely typed programming language can be characterized as below:

  • It does not require the specification of the data types in variables.
  • It allows conversions between unrelated data types.
  • Conversion between different types is performed implicitly at run-time.
  • It does not contain compile or run-time checks for type constraint violations
  • It has less strict typing rules.

A major advantage of loosely typed programming languages is flexibility. While working with dynamic applications, there are a lot of actions that happen based on unknown data. The ability for the implicit type conversion allows for flexibility.

Another advantage is the simplicity. Due to its loose typing rules, learning and working with PHP is pretty much straightforward and simple as opposed to strongly typed languages such as Java or C.

A disadvantage of a loosely typed language is that it may produce unpredictable or even erroneous results at run-time. For instance, when an integer value is expected in a calculation but instead a string value is passed instead. You can prevent this by validating the type of data before performing certain operations.