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. 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. $myVariable
A variable is used in programming to represent another value. In PHP variables all start with a dollar sign ($). They can be set to a string or a numeric value.
Code: <?php
$a = "Alexa"; //This sets the variable $a to a string value (Alexa)
$b = 6; //This sets the variable $b equal to a number value (6)
?> You will notice that string values are contained with quotations [""] while numeric values are not. Instaed of just a static number, you can also set a variable equal to an equation. Here are some examples:
Code: <?php
$a = 3 + 5; //This sets the variable $a equal to 8 or (3 + 5)
$b = 6 + $a; //This sets the variable $b equal to 14, or (6 + $a)
?>
We can combine values using a period [.] This will literally mash the values together. Here are some examples:
Code: <?php
$a = 1;
$b = 2;
$c = $a.$b;
//The value of $c is now 12, because we smashed the 1 and 2 together
$d= $c + 1 ;
echo $d;
// This will echo 13, our newly created 12 plus 1 is 13
$e = "Number";
$f = $e.$d;
echo $f;
//This will echo the string Number13, a combination of $e and $f
?> This is different than just echoing both variables as a new variable is actually created from the other variables. Another thing you can do is make a variable from a string by using {} symbols. So, by using this method you could pass a string from one page to another, and use that string to pull the information from a variable of the same name. Here is an example: Code: <?php
$a= "SomeVar";
$SomeVar= "test";
echo ${$a};
?>
This will return "test", which is the value of $SomeVar because by using the {} symbols we are creating the variable from the string in $a.
Note: PHP does not require variables to be declared before being initialized.
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Variables