PHP Loops

PHP break keyword

In PHP, break can be used to terminate execution of a for, foreach, while or do…while loop.

One downside of heavy usage of break statements is that code can become less readable.

// We can use the break statement to end the loop once the count reaches 4
$count = 1;
while ($count < 10)
{
  echo "The count is: " . $count . "\n";
  if ($count === 4) {
    break;
  }
  $count += 1;
}

PHP do while loops

In PHP, do…while loops are very similar to while loops. The main difference is that do...while loops always execute their code block at least once and continue execution as long as their conditional statement is true. Even if the conditional is false, the code block will execute one time.

The syntax for a do…while loop is:

do {
    #code block
} while (/*conditional*/);

// This loop counts from 0 to 100
$count = 0;
do {
  echo "The count is: " . $count . "\n";
  $count += 1;
} while ($count <= 100);

PHP for loop

In PHP, a for loop is commonly used to execute a code block a specific number of times. The syntax makes use of three expressions:

for (#expression 1; #expression 2; #expression 3)
{
  # code block
}

The first is evaluated only one time before the first iteration
The second is evaluated before each iteration. If it is TRUE, the code block is executed. Otherwise, the loop terminates.
The third is evaluated after each iteration.

// This for loop counts from 1 to 50
for ($count = 1; $count < 51; $count++)
{
  echo "The count is: " . $count . "\n";
}

PHP while loops

In PHP, while loops repeat execution of their code block as long as their conditional statement is true.

The syntax for a while loop is:

while (/*conditional*/) {
  #code block
}

// This while loop counts from 0 to 100
$count = 0;
while ($count <= 100)
{
  echo "The count is: " . $count . "\n";
  $count += 1;
}

PHP foreach loop

In PHP, the foreach loop is used for iterating over an array. The code block is executed for every element in the array and the value of that element is available for use in the code block.

The syntax is:

foreach ($array as $value) {
  #code block
}

On each iteration, a $value from $array is available for usage in the code block.

To access the keys as well as values in an array, the syntax can be modified to:

foreach ($array as $key => $value) {
  #code block
}

// This foreach loop counts from 1 to 5
$nums = [1, 2, 3, 4, 5];
foreach ($nums as $num) {
  echo "The num is: " . $num . "\n";
}

PHP continue keyword

In PHP, continue can be used to terminate execution of a loop iteration during a for, foreach, while or do…while loop. The code execution continues with the next iteration of the loop.

The continue keyword is similar to break except it only ends the current iteration early, not the entire loop.

// This code counts from 1 to 10 but skips over 5
$count = 1;
while ($count < 11)
{
  if ($count === 5) {
    $count += 1;
    continue;
  }
  echo "The count is: " . $count . "\n";
  $count += 1;
}