feat: variable scopes

Author: codewithhridoy

05_variable_scopes.php

@@ -0,0 +1,97 @@
+<?php
+
+/*
+ * PHP has three different variable scopes:
+ * local, global & static
+ * */
+
+/*
+ * Local Scope
+ *  A variable declared within a function has a LOCAL SCOPE.
+ *  and can only be accessed within that function.
+ * */
+
+function showFullName(): string
+{
+    $first_name = 'Hridoy';
+    $last_name  = 'Ahmed';
+
+    return $first_name . ' ' . $last_name;
+}
+
+$full_name = showFullName();
+
+echo '<pre>';
+print_r($full_name);
+
+echo '<pre>';
+// print_r($first_name);
+// If you comment out the above line will give you a warning.
+// Because You Cannot access first_name outside the function as it is a local variable.
+
+
+/*
+ * Global Scope
+ *  The global keyword is used to access a global variable from within a function.
+ *  If you update the global variables inside a function it will overwrite the original variable's value.
+ *  PHP also stores all global variables in an array called $GLOBALS[index].
+ *  The index holds the name of the variable.
+ *  This array is also accessible from within functions.
+ *  Can be used to update global variables directly.
+ * */
+
+$a = 10;
+$b = 20;
+$c = 30;
+
+function testGlobal(): void
+{
+    global $a, $b, $c;
+
+    echo '<p>' . 'Without Updating Global Variable Sum = ' . $a + $b + $c . '</p>';
+
+    $a = 100; // Update the global variable
+    $b = 200;
+    $c = 300;
+
+    echo '<p>' . 'After Updating the values of the global varibles Sum = ' . $a + $b + $c . '</p>';
+}
+
+testGlobal();
+
+// Using GLOBALS
+$x = 5;
+$y = 10;
+
+function testGlobal2(): void
+{
+    $GLOBALS['y'] = $GLOBALS['x'] + $GLOBALS['y'];
+}
+
+testGlobal2();
+echo '<pre>';
+echo $y; // outputs 15
+
+/*
+ * Static Scope
+ *  Normally, when a function is completed/executed, all of its variables are deleted.
+ *  If you update the static variables inside a function it will overwrite the original variable's value.
+ *  If you want a local variable NOT to be deleted, you can use the static keyword.
+ *  Note: The variable is still local to the function.
+ */
+
+function testStatic(): void
+{
+    static $x = 0; // Remember the value for the next usage.
+    echo $x;
+    $x++;
+}
+
+echo '<pre>';
+testStatic();
+
+echo '<pre>';
+testStatic();
+
+echo '<pre>';
+testStatic();