PHP – Variables

If you have never had any programming, Algebra, or scripting experience, then the concept of variables might be a new concept to you. A detailed explanation of variables is beyond the scope of this tutorial, but we've included a refresher crash course to guide you.


A variable is a means of storing a value, such as text string "Hello World!" or the integer value 4. A variable can then be reused throughout your code, instead of having to type out the actual value over and over again. In PHP you define a variable with the following form:



$variable_name = Value;

If you forget that dollar sign at the beginning, it will not work. This is a common mistake for new PHP programmers!



Note: Also, variable names are case-sensitive, so use the exact same capitalization when using a variable. The variables $a_number and $A_number are different variables in PHP's eyes.




A Quick Variable Example



Say that we wanted to store the values that we talked about in the above paragraph. How would we go about doing this? We would first want to make a variable name and then set that equal to the value we want. See our example below for the correct way to do this.



PHP Code:









Note for programmers: PHP does not require variables to be declared before being initialized.


PHP Variable Naming Conventions



There are a few rules that you need to follow when choosing a name for your PHP variables.



PHP variables must start with a letter or underscore "_".

PHP variables may only be comprised of alpha-numeric characters and underscores. a-z, A-Z, 0-9, or _ .

Variables with more than one word should be separated with underscores. $my_variable

Variables with more than one word can also be distinguished with capitalization. $myVariable


PHP – Echo



As you saw in the previous lesson, the PHP command echo is a means of outputting text to the web browser. Throughout your PHP career you will be using the echo command more than any other. So let's give it a solid perusal!


Outputting a String



To output a string, like we have done in previous lessons, use PHP echo. You can place either a string variable or you can use quotes, like we do below, to create a string that the echo function will output.



PHP Code:

I love using PHP!";

?>



Display:



Hello!

I love using PHP!

In the above example we output "Hello!" without a hitch. The text we are outputting is being sent to the user in the form of a web page, so it is important that we use proper HTML syntax!



In our second echo statement we use echo to write a valid Header 5 HTML statement. To do this we simply put the

at the beginning of the string and closed it at the end of the string. Just because you're using PHP to make web pages does not mean you can forget about HTML syntax!


Careful When Echoing Quotes!



It is pretty cool that you can output HTML with PHP. However, you must be careful when using HTML code or any other string that includes quotes! Echo uses quotes to define the beginning and end of the string, so you must use one of the following tactics if your string contains quotations:


Don't use quotes inside your string

Escape your quotes that are within the string with a backslash. To escape a quote just place a backslash directly before the quotation mark, i.e. \"

Use single quotes (apostrophes) for quotes inside your string.

See our example below for the right and wrong use of echo:



PHP Code:

I love using PHP!

";



// OK because we escaped the quotes!

echo "

I love using PHP!

";



// OK because we used an apostrophe '

echo "

I love using PHP!

";

?>



If you want to output a string that includes quotations, either use an apostrophe ( ' ) or escape the quotations by placing a backslash in front of it ( \" ). The backslash will tell PHP that you want the quotation to be used within the string and NOT to be used to end echo's string.


Echoing Variables

Echoing variables is very easy. The PHP developers put in some extra work to make the common task of echoing all variables nearly foolproof! No quotations are required, even if the variable does not hold a string. Below is the correct format for echoing a variable.



PHP Code:





Display:

Hello Bob. My name is: 4a

Echoing Variables and Text Strings

You can also place variables inside of double-quoted strings (e.g. "string here and a $variable"). By putting a variable inside the quotes (" ") you are telling PHP that you want it to grab the string value of that variable and use it in the string. The example below shows an example of this cool feature.



PHP Code:

";

echo "Hi, I'm Bob. Who are you? $my_string
";

echo "Hi, I'm Bob. Who are you? $my_string Bobetta";

?>



Display:



Hello Bob. My name is: Bobetta

Hi, I'm Bob. Who are you? Hello Bob. My name is:

Hi, I'm Bob. Who are you? Hello Bob. My name is: Bobetta



By placing variables inside a string you can save yourself some time and make your code easier to read, though it does take some getting used to. Remember to use double-quotes, single-quotes will not grab the value of the string. Single-quotes will just output the variable name to the string, like )$my_string), rather than (Hello Bob. My name is: ).


PHP Echo - Not a Function



Echo is not a function, rather it is a language construct. When you use functions in PHP, they have a very particular form, which we will be going over later. For now, just know that echo is a special tool that you'll come to know and love!