Create different variables

                
<?php
    $txt = "Hello world!";
    $x = 5;
    $y = 10.5;
    
    echo $txt;
    echo "<br>";
    echo $x;
    echo "<br>";
    echo $y;
?>
                
                

Test global scope (variable outside function)

                
<?php
    $x = 5; // global scope
        
    function myTest() {
        // using x inside this function will generate an error
        echo "<p>Variable x inside function is: $x</p>";
    } 
    myTest();
    
    echo "<p>Variable x outside function is: $x</p>";
?>
                
                

Test local scope (variable inside function)

    <?php
    function myTest() {
        $x = 5; // local scope
        echo "<p>Variable x inside function is: $x</p>";
    } 
    myTest();
    
    // using x outside the function will generate an error
    echo "<p>Variable x outside function is: $x</p>";
?>
                
                

Use the global keyword to access a global variable from within a function

                
<?php
    $x = 5;
    $y = 10;
    
    function myTest() {
        global $x, $y;
        $y = $x + $y;
    } 
    
    myTest();  // run function
    echo $y; // output the new value for variable $y
?>
                
                

Use the $GLOBALS[] array to access a global variable from within a function

                
<?php
    $x = 5;
    $y = 10;
    
    function myTest() {
        $GLOBALS['y'] = $GLOBALS['x'] + $GLOBALS['y'];
    } 
    
    myTest();
    echo $y;
?>
                
                

Use the static keyword to let a local variable not be deleted after execution of function

                
<?php
    function myTest() {
        static $x = 0;
        echo $x;
        $x++;
    }
    
    myTest();
    echo "<br>";
    myTest();
    echo "<br>";
    myTest();
?>