Global namespace access in PHP - Step-by-Step Execution

Concept Flow - Global namespace access

Start script

↓

Define global variable

↓

Enter function

↓

Access global variable using $GLOBALS or global keyword

↓

Modify or read global variable

↓

Exit function

↓

Use global variable outside function

↓

End script

The script defines a global variable, then inside a function accesses it using special ways, modifies or reads it, then continues outside the function.

Execution Sample

PHP

<?php
$val = 10;
function test() {
  global $val;
  $val += 5;
}
test();
echo $val;
?>

This code shows how to access and modify a global variable inside a function using the global keyword.

Execution Table

Step	Action	Variable	Value	Notes
1	Define global variable	$val	10	Global scope
2	Enter function test()	-	-	Function starts
3	Declare global $val inside function	$val	10	Access global variable
4	Modify $val inside function	$val	15	Increment by 5
5	Exit function test()	-	-	Function ends
6	Echo $val	$val	15	Global variable updated
7	End script	-	-	Script ends

💡 Script ends after printing updated global variable value 15

Variable Tracker

Variable	Start	After function call	Final
$val	10	15	15

Key Moments - 2 Insights

Why do we need the 'global' keyword inside the function?

Without 'global', the function treats $val as a new local variable. Using 'global $val' tells PHP to use the variable from the global scope, as shown in step 3 of the execution_table.

Can we access global variables inside functions without 'global'?

Yes, by using the $GLOBALS array like $GLOBALS['val'], but this example uses 'global' keyword for simplicity (not shown in this trace).

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of $val after step 4?

A 15

B 10

C 5

D Undefined

💡 Hint

Check the 'Modify $val inside function' row in execution_table where $val changes to 15.

At which step does the function test() end?

A Step 3

B Step 4

C Step 5

D Step 6

💡 Hint

Look for the row with 'Exit function test()' in execution_table.

If we remove the 'global $val;' line, what would be the output at step 6?

A 15

B 10

C Error

D 5

💡 Hint

Without 'global', $val inside function is local and global $val remains unchanged as in variable_tracker.

Concept Snapshot

PHP global namespace access:
- Global variables exist outside functions.
- Use 'global $var;' inside functions to access global variables.
- Alternatively, use $GLOBALS['var'] array.
- Without this, functions use local variables.
- Changes inside function affect global variable if accessed properly.

Full Transcript

This example shows how PHP handles global variables inside functions. We start with a global variable $val set to 10. Inside the function test(), we use the 'global' keyword to tell PHP to use the global $val, not a new local one. We then add 5 to $val, making it 15. After the function ends, when we echo $val, it prints 15, showing the global variable was updated. Without 'global', the function would create a local $val and the global $val would stay 10. This trace helps understand how to access and modify global variables inside functions in PHP.