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Variables serve as containers to hold various types of information or data that we can utilize throughout our program. For instance, imagine having a variable to store a user’s email address and then being able to retrieve and use that email later on in the program.
So, how do we create these variables? Well, it’s quite simple. We begin by using the dollar sign ($) followed by the variable name. For example, if we wish to store someone’s age, we could name our variable “age”. However, there are some rules to follow when naming variables.
Variables must start with a letter or an underscore, followed by a combination of letters (uppercase or lowercase), underscores, or numbers. They cannot begin with numbers or special characters.
Now, let’s talk about camel case variable naming convention. This means if a variable has two words, like “firstName”, the first letter of the second word is capitalized. Alternatively, you can separate words with underscores. It’s all about personal preference and readability.
For now, let’s create a variable named “name” and set it equal to a string, such as “Yoshi”. Strings are sequences of characters enclosed in quotes, either single or double.
$name = “Yoshi”;
To access this variable later, we simply use echo $name.
echo $name;
This will output “Yoshi” to the screen.
Now, let’s create another variable, “age”, and set it equal to an integer, like 30.
$age = 30;
Unlike strings, integers do not require quotes. We can output the age the same way we did with the name variable.
echo $age;
Now, here’s an important point: variables can be overridden. For instance, if we set $name to “Mario” later in the program, it will replace the previous value of “Yoshi”.
$name = “Mario”;
Now, accessing $name will output “Mario”.
echo $name;
But what if you want a value to remain constant and not be overridden? Enter constants.
Constants are defined using the define() function. You specify the constant name in uppercase and assign it a value
define(“NAME”, “Yoshi”);
To access a constant, you don’t use the dollar sign ($). Instead, you simply refer to the constant name.
echo NAME
Constants cannot be redefined once set. Attempting to do so will result in an error.
define(“NAME”, “Mario”); // This will cause an error
In summary, variables are containers for storing data, and constants are for defining values that remain constant throughout the program execution. Understanding how to use and manipulate variables and constants is essential for PHP development.