PHP 7 Variables

A variable is a name or symbol that contains a value. We assign a value to a variable and that variable become reference to the assigned value.

Declaring a variable

<?php
   $a1 = 10;
   $a2 = "Good Morning!";
?>

In the above example, $a1 and $a2 are variables. The variable $a1 holds the number value 10 and $a2 holds the string value 'Good Morning!'.

These are some useful features of PHP variables-

  • It does not need to define a datatype of a variable before assign them to a value.
  • We cannot say the variable is used for which data type integer or string or boolean. So we can easily convert from one data type into another.
  • In PHP, by default a variable has null value.
  • In PHP, a variable leads with a dollar ($) sign and then can be starts with a letter or underscore (_), means first letter should be (A-Za-z) or (_), then you can use as many alphanumerics and characters. These are valid variable examples in PHP.
    $var
    $var1
    $_var
    $_var23
  • Using equal to (=) assignment operator, we can assign value to a variable.
  • PHP variable names are case sensitive.
  • The value of a variable is the value of its most recent assignment.
Example -
<?php
    $var = 23;
    $var1 = 'Welcome to eTutorial';
    $_var = 15.5;
?>




Scopes of PHP 7 variables

PHP variable has two scopes - Global and Local.

Global Scope -

PHP variable declares outside of a function has global scope. The value of the variable has remained same until it is not reassigned other value.

Local Scope -

PHP variable declares inside a function has local scope.

If a variable with the same name is declared inside and outside of the function, then both are considered as different.

Example -

<?php
 $var = 100;
 function demo() {
   $var = 50;
   echo $var;
 }
 demo();
 echo '<br/>';
 echo $var;
?>
In the above example, first value assign to $var has global scope wheras the value assign to $var within demo() function has local scope.

The output of the above example is -
50
100

Checking PHP variable assignment

PHP variables do not have to be assigned before use, in some situations you can actually convey information by selecting setting or not setting a variable. PHP provides a function called isset that tests a variable to see whether it has been assigned a value or not.

Example -
$my_var = 'check assignment';
if(isset($my_var)) {
echo 'my_var is set';
} else {
echo 'my_var is not set';
}


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