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(); 
?>

Post a Comment

If you have any doubts, Please let me know
Thanks!

Previous Post Next Post