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:
1 |
$firstName = 'KRITIKA'; $number = 24; |
This value of a variable can come from:
-
- User input from an online form.
- From a database
- From PHP file itself.
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$firstName = 'KRITIKA'; $number = 24; echo $firstName; print $number; |
- 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 | |
---|---|
echo has no return value | print has a return value of 1 |
echo can take multiple parameters | print can take one argument |
echo Example:
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echo "This ", "is ", "a ", "string ", "made ", "with multiple parameters."; |
Output:
This is a string made with multiple parameters.
print Example:
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print "This ", "is ", "a ", "string", "made ", "with multiple parameters."; |
Output:
FATAL ERROR syntax error, unexpected ‘,’ on line number 2