Development Php

$var1 = 'PHP';          
$var2 = 5;              
$var3 = $var2 + 1;      
$var2 = $var1;          
echo($var1);            
echo($var2);            
echo($var3);            
echo($var1 . ' rules!');
echo("$var1 rules!");   
echo('$var1 rules!');   
?>