One of the basic elements of any programming language (including PHP ) are certainly the variables .
What is a variable?
The variable can be defined as a memory area in which information is saved (to which the programmer assigns a particular identifier) which can change during the processing phase of the program itself.
In PHP all variables start with a dollar sign ( $ ). The value of a variable is assigned with an “equal” ( = ).
Let’s see an example of a text variable (more correctly defined as a string variable:
//String Variable Syntax $variable = "String Here.."; //Example $name = "Mr, Jon";
If your variable, on the other hand, had a numeric value (so-called numeric variables ). The quotation marks would not be necessary; here is an example:
//String Variable Syntax $variable = 123; //Example $age = 25; $pi = 3.14;
Another type of variable widely used is the Boolean variable. We say “boolean” a variable that can have only “true” ( true ) or “false” ( false ) as its value:
// variable booleana if value true $variabile = true; // variable booleana if value false $variabile = false;
Print the Value of a Variable on The Screen
Through the variables, we can perform various operations such as for example, mathematical calculations or comparisons. The simplest thing we can do with a variable is to print its content on the screen (obviously this operation does not make sense for Boolean type variables).
So let’s see a simple PHP code that uses variables and the echo command to print the value of a variable on the screen:
<?php $name = "Mr. Joy"; echo $name; ?>
Warning : the variable names are case sensitive … therefore pay attention to upper and lower case!
Let’s take another example:
<?php $name = "Mr. Joy"; $age = 25; echo "Name: ". $name; echo " Age: ". $age; ?>
In the latter example we have printed a sentence on the screen inside which there are two variables.
In the example above, we used two variables and printed them on the screen within a sentence. As you may have noticed, we used the dot ( . ) To join the different parts of the sentence together. The dot, in fact, is used in PHP as a concatenation operator.
<?php $var1 = "Hello"; $var2 = "World!"; echo $var1 . $var2; ?>
It is hardly necessary to underline how, in the example above, the contents of the variables will be printed on the screen without any space. If we had wanted to add a space between one variable and another we would have had to write:
<?php $var1 = "Hello"; $var2 = "World!"; echo $var1 . " " . $var2; ?>
A particular case is when you want to change the value of a variable using the concatenation operator.