PHP Variables
• As with algebra, PHP variables can be used to hold values (x=5) or expressions
(z=x+y).
• A variable can have a short name (like x and y) or a more descriptive name (age,
carname, total_volume).
• Rules for PHP variables:
o A variable starts with the $ sign, followed by the name of the variable
o A variable name must start with a letter or the underscore character
o A variable name cannot start with a number
o A variable name can only contain alpha-numeric characters and underscores
(A-z, 0-9, and _ )
o Variable names are case sensitive ($y and $Y are two different variables)
Creating (Declaring) PHP Variables
• PHP has no command for declaring a variable.
• A variable is created the moment you first assign a value to it:
Example:-
<?php
$txt="Hello world!";
$x=5;
$y=10.5;
?>
PHP Variables Scope
• In PHP, variables can be declared anywhere in the script.
• The scope of a variable is the part of the script where the variable can be
referenced/used.
• PHP has three different variable scopes:
o local
o global
o static
Local and Global Scope
• A variable declared outside a function has a GLOBAL SCOPE and can only be
accessed outside a function.
• A variable declared within a function has a LOCAL SCOPE and can only be
accessed within that function.
• The following example tests variables with local and global scope:
Example
<?php
$x=5; // global scope
function myTest() {
$y=10; // local scope
echo "<p>Test variables inside the function:</p>";
echo "Variable x is: $x";
echo "<br>";
echo "Variable y is: $y";
}
myTest();
echo "<p>Test variables outside the function:</p>";
echo "Variable x is: $x";
echo "<br>";
echo "Variable y is: $y";
?>
PHP The global Keyword
• The global keyword is used to access a global variable from within a function.
• To do this, use the global keyword before the variables (inside the function):
Example
<?php
$x=5;
$y=10;
function myTest() {
global $x,$y;
$y=$x+$y;
}
myTest();
echo $y; // outputs 15
?>
PHP The static Keyword
• Normally, when a function is completed / executed, all of its variables are deleted.
However, sometimes we want a local variable NOT to be deleted. We need it for a
further job.
• To do this, use the static keyword when you first declare the variable:
Example
<?php
function myTest() {
static $x=0;
echo $x;
$x++;
}
myTest();
myTest();
myTest();
?>
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