PHP Loops: Types with Examples

PHP Loops are used to execute a block of code multiple times based on a given condition. Explore the types of PHP Loops – for, while & foreach loops with syntax and examples:

In this tutorial, you will learn what loops are, the types of loops (PHP while, PHP do while, PHP for, & PHP foreach), differences between while & do-while, differences between for & foreach, and frequently asked questions (FAQs). Please note that we have used PHP version 7 in all examples.

Let’s begin!

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Introduction to PHP Loops

The function of a loop is to execute the same code block a specified number of times. It is also referred to as a repetition statement. Furthermore, it can be nested too.

Types of Loops in PHP

There are four loops in PHP, as shown in the list below:

1. While
2. Do-while
3. For
4. Foreach

PHP While Loop

PHP while loop iterates through a code block as long as the specified condition is true. It is also the simplest type.

Syntax:

while(condition){  
  //code to be executed 
}  

Alternatively, you may use the following syntax.

while(condition):  
  //code to be executed 
endwhile;

A few examples are shown below. You can practise these examples by running the following programming code.

Example 1:

<?php

$num = 1;

while($num <= 3){
    echo "Hello! <br/>";
    $num++;
}

?>

Output:

Hello!
Hello!
Hello!

Note: In the above example, there will be no output if the specified condition is false at the very beginning.

Example 2:

<?php

$num = 1;

while($num <= 5){
    echo "$num <br/>";
    $num++;
}

?>

Output:

1
2
3
4
5

Example 3:

<?php

$num = 8;

while($num <= 5){
    echo "$num <br/>";
    $num++;
}

?>

The above programming code does not have any output as the specified condition is false at the very beginning.

PHP Do While Loop

PHP do-while iterates through a code block once and then continues the loop as long as the specified condition is true. The do-while loop is guaranteed to execute a minimum of once.

Syntax:

do{

code to be executed;

}while (condition);

A few examples are shown below. You can practise these examples by running the following programming code.

Example 1:

<?php

$num = 1;

do{
  echo "$num<br>";
  $num++;
}while($num <= 5);

?>

Output:

1
2
3
4
5

Example 2:

<?php

$num = 5;

do{
  echo "$num<br>";
  $num--;
}while($num >= 1);

?>

Output:

5
4
3
2
1

Example 3:

<?php

$num = 20;

do{
  echo "$num<br>";
  $num++;
}while($num <= 5);

?>

Output:

20

While vs Do-while

Both while and do-while are similar to each other. However, there are some differences too.

The major difference between while and do-while is that do-while always executes once, even if the specified condition is false. But while loop evaluates the specified condition at the beginning and only executes if the condition is true.

The table below shows the difference between while and do-while.

PHP For Loop

PHP for loop iterates through a code block a specified number of times.

Syntax:

for(init counter; test counter; increment/decrement counter){

code to be executed

}

An example is given below. You can practise this example by running the following programming code.

<?php

for($num = 1; $num <= 5; $num++){
  echo "$num<br>";
}

?>

Output:

1
2
3
4
5

PHP Foreach Loop

PHP foreach iterates through a code block for each element in an array data structure.

Syntax:

foreach($array as $value){

code to be executed;

}

Alternatively, you may use the following syntax (please see example 2 below).

foreach ($array as $key => $value) {

code to be executed;

}

A few examples are shown below. You can practise these examples by running the following programming code.

Example 1:

<?php

$value = array("HTML", "CSS", "JS");

foreach($value as $val){
  echo "$val <br>";
}

?>  

Output:

HTML
CSS
JS

Example 2:

<?php

$signals = array("Red"=>"Stop!", "Yellow"=>"Wait!", "Green"=>"Go!");

foreach($signals as $sign => $value){
  echo "$sign = $value<br>";
}

?>

Output:

Red = Stop!
Yellow = Wait!
Green = Go!

For vs Foreach

Both for and foreach are similar to each other. But, there are significant differences too.

The below table shows the difference between for and foreach.

Break and Continue Keywords

The Break Keyword

We have already covered the break keyword in our previous tutorial. However, we are going to look at how the break keyword can be used in loops.

The break keyword is used to immediately end the execution of a loop.

In a nested loop, the break keyword ends the execution of the loop where the break is placed. If the break keyword is placed in the inner loop, then the outer loop still can be executed. But if the break is placed in the outer loop, then it will stop the outer loop as well as the inner loop(s).

Let’s see a few examples. You can practise these examples by running the following programming code.

Example 1:

<?php  

for($num = 1; $num < 5; $num++){
  if($num == 3){
    break;
  }
  echo "Number $num <br>";
}

?>

Output:

Number 1
Number 2

Example 2:

<?php  

$num = 1;

while($num < 5){
  if($num == 3){
    break;
  }
  echo "Number $num <br>";
  $num++;
}

?>

Output:

Number 1
Number 2

The Continue Keyword

The continue keyword is used to go to the next iteration of a loop.

Let’s see a few examples. You can practise these examples by running the following programming code.

Example 1:

<?php  

for($num = 1; $num < 5; $num++){
  if($num == 3){
    continue;
  }
  echo "Number $num <br>";
}

?>

Output:

Number 1
Number 2
Number 4

Example 2:

<?php  

$num = 1;

while($num < 5){
  if ($num == 3){
  	$num++;
    continue;
  }
  echo "Number $num <br>";
  $num++;
}

?>

Output:

Number 1
Number 2
Number 4

Frequently Asked Questions (FAQs)

Conclusion

A loop or a repetition statement executes the same code block a specified number of times. There are four loops in PHP: while, do-while, for, and foreach.

The break keyword is used to immediately end the execution of a loop, while the continue keyword is used to go to the next iteration of a loop.

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