4) PHP Variables

What are Variables?

Variables are a fundamental building block of all programming languages. A variable is simply a placeholder for a value that you don’t know or that might change. The name of the variable remains the same but its value can change.

Naming Variables:

  • In PHP variable always begin with a $ sign.
  • Any combination of letters, number or underscore are valid.
  • The first character after $ sign must not be a number.
  • No spaces or hyphens are allowed.
  • Names are case-sensitive.

Good Naming Practice

  • Choose meaningful names.
  • Don’t use short letters, except for counters.
  • A good variable name makes your code easy to understand and maintain.
  • Use camelcase or underscore for multiple words. Ex: $firstName, $first_name
  • Make sure variables are case sensitive so $firstname is not same as $firstName.

Reserved Names:

$this -> is reserved variable for PHP object-oriented script. Check the list of all reserved variables here and avoid using them.

Example variable:

This value of a variable can come from:

    • User input from an online form.
    • From a database
    • From PHP file itself.

  • We assign the value to a variable by the assignment operator, which is simply an equal sign.
  • The $firstname in the example above is a text and text is always written in quotes and after quotes, we put a semicolon. In computing terminology text is referred to as a string. So datatype of a variable is a string in above example. In PHP you do not need to specify a type of data stored by a variable in PHP.
  • Another variable is $number. Numbers are not in quotes and can be in decimal.
  • We have two variables in our code try to load them in a browser.

Difference between Print and echo

echo and print are basic ways to get output.
There is not much difference between echo and print.

Echo Print
echo has no return value print has a return value of 1
echo can take multiple parameters print can take one argument

echo Example:

Output:
This is a string made with multiple parameters.

print Example:

Output:
FATAL ERROR syntax error, unexpected ‘,’ on line number 2