Loop iteration refers to a single cycle within a loop, during which a specific block of code is executed. 

PHP Loop Control Structures

In PHP programming, there are two primary loop control structures. 

Break in PHP

The ‘break’ statement in PHP is used to terminate the current loop prematurely. It stops the execution of the loop and moves control to the statement immediately following the loop.

Example of PHP Break

In this example, the loop will stop once the variable `$a` reaches the value of 5:

```php
$a = 0;
while ($a < 10) {
	echo $a . '<br>';
	if ($a === 5) {
		break;
	}
	$a++;
}
```

Advanced Usage of Break

PHP allows the use of an optional numeric argument with the ‘break’ statement, enabling the termination of multiple nested loops. For instance, ‘break 2;’ will terminate two levels of nested loops.

Nested Loop Break Example

Here’s an example demonstrating breaking out of two nested loops in PHP:

```php
for ($a = 0; $a < 10; $a++) {
	echo "$";
	for ($b = 0; $b < 10; $b++) {
		if ($a === 3 && $b === 5) {
			echo '<br> Breaking two loops';
			break 2;
		}
		echo $b;
	}
	echo '<br>';
}
```

Continue in PHP

The ‘continue’ statement in PHP skips the remaining part of a loop iteration and proceeds to the next iteration after reevaluating the loop condition.

Example of PHP Continue

In the following example, the ‘continue’ statement is used to skip printing the number 5:

```php
$a = 0;
while ($a < 10) {
	if ($a === 5) {
		$a++;
		continue;
	}
	echo $a . '<br>';
	$a++;
}
```

Extendibility of Continue

Similar to ‘break’, ‘continue’ can also include a numeric argument to affect multiple nested loops.

Additional Notes

Both ‘break’ and ‘continue’ can be applied in switch statements in PHP, offering additional control in various coding scenarios.

Conclusion

In summary, understanding and effectively utilizing loop control structures like ‘break’ and ‘continue’ in PHP is crucial for any developer aiming to write efficient and readable code. The ‘break’ statement serves as a powerful tool for terminating loop execution when a specific condition is met, thereby preventing unnecessary iterations and potentially enhancing program performance. On the other hand, ‘continue’ allows for the selective skipping of loop iterations, enabling more complex and nuanced control flow within loops. These structures not only streamline the coding process but also offer a level of precision in execution control that can be pivotal in complex programming scenarios. Particularly in the context of nested loops, the ability to specify the number of loops to be affected adds a layer of sophistication to these control structures. Ultimately, the judicious use of ‘break’ and ‘continue’ in PHP loops leads to more efficient, maintainable, and effective code, reflecting best practices in programming.