6 ways to loop through an array in php

By Parth Patel on Sep 11, 2021

Today, we will learn how to loop through an array in PHP using while ****loop, for loop, & various PHP Array functions.

PHP is one of the easiest language and traversing through an array in php is very easy. Infact, most popular way to access items in array in php is using loops : while, for & do..while

Let's jump into it:

1. While loop

The while loop is very common loop among all languages and PHP is not different. In fact, while loop is one of the most popular method to iterate over PHP array.

Let's checkout the syntax:

Syntax:

while(expression){
    // Code to be executed
}

It means that, while the given expression (or condition) is true, execute the code inside the curly brackets, and check the expression again. Keep doing it, until expression becomes false.

How to Iterate over PHP array using while loop

The PHP arrays have elements which can be accessed via its index position, right?

So, we can use the while loop to change the index position incrementally or decrementally therefore accessing every element (or selective elements as per the condition).

Let's see how it works,

Example:

Here, we will create an index position variable and start with 0th position which is first in an array.

The condition will be to continue fetching element from an array til our index values is less than the count of array (or length of the given array).

Since, while loop will not increment our index variable automatically, we need to increment it inside the loop. Therefore, with each iteration, variable will move to next index position.

<?php
$users = ['john', 'dave', 'tim'];

$i = 0;

while($i < count($users))
{
	echo $users[$i]."\n";
	$i++;
}
?>

Output:

john
dave
tim

2. do while Loop

Well, personally it's my least favorite loop in every programming language, so I'd probably say less.

The do while is another type of loop in php (and mostly all programming languages ... except some functional languages .. Yes, I am looking at you Smalltalk )

It is mostly similar to while loop, except the ordering is reverse.

In while loop, condition or expression is checked first & if true, then the code inside the loop gets executed
In do while loop, code inside the loop gets executed first & then the condition is checked. If condition is true, then it will execute the code again and so on.

Let's checkout the syntax:

Syntax:

do {
	// Code to be executed
}
while(expression);

It means that, while the given expression (or condition) is true, execute the code inside the curly brackets, and check the expression again. Keep doing it, until expression becomes false.

Note: Don't miss the semicolon at the end. I always forget that.

Without further ado, let's recrete previous example using do while loop

How to loop through php array using do while loop

We will iterate over an array of users using do while loop.

Example:

<?php
$users = ['john', 'dave', 'tim'];

$i = 0;

do
{
	echo $users[$i]."\n";
	$i++;
}
while($i < count($users));
?>

Output:

john
dave
tim

3. For Loop

Let's talk about the MOST popular loop. The for loop.

The for loop is my most favorite general loop (next one I use often for this particular usecase) for any general iterative usecase. It does the exactly same as while loop but it has different, more compact syntax.

Syntax:

for (expr1; expr2; expr3) {
	//Code to be executed
}

It looks very complex at first, but when you get bit experience, believe me, you will prefer this most of the time.

It has placeholder for three expressions (each are optional, so you can still use this loop just like while)

Expr1 - It gets executed once at the beginning of the loop, so normally it is used to initialize any counters to be used.
Expr2 - This is the condition part. At the beginning of each iteration, this expression gets evaluated and if true then only it will continue.
Expr3 - It gets execute at the end of the iteration. Normally used to increment/decrement our counters.

Let's recreate our example using for loop.

How to loop through array using for loop in PHP

As shown below, it is exactly same as while loop, except it's condensed and better syntax. Also, for one line statements, you can omit curly brackets ;)

<?php
$users = ['john', 'dave', 'tim'];

for($i = 0;$i < count($users);$i++)
	echo $users[$i]."\n";
?>

Output:

john
dave
tim

4. Foreach Loop

Talking about condensed syntax, let's talk about another great and special loop - Foreach loop.

This loop is only helpful when you want to iterate over each item. If for example - you want to access only even position items, then sadly this loop is not for you, you need to use above loops.

But, for the particular use of accessing each item (see the pun?), foreach is my favorite and infact would be everyone's favorite. It is very simply and easy to use.

Syntax:

//without key
foreach (iterable_expression as $value)
    statement

//with key
foreach (iterable_expression as $key => $value)
    statement

Let's checkout the example:

How to loop over array using foreach loop in PHP

Let's recreate our example. We won't need the keys (position) therefore we will use foreach without keys.

<?php

$users = ['john', 'dave', 'tim'];

foreach($users as $user)
	echo $user."\n";
?>

Output:

john
dave
tim

5. array_walk

The array_walk is an array function provided by PHP which applies the given function to each element in the array, hence the name "array_walk".

Syntax:

array_walk(array|object &$array, callable $callback, mixed $arg = null): bool

Parameters:

array - It is the input array to iterate over.
callback - It is a function passed to this function which will act on each item one by one. This function takes two parameters - 1. Item value 2. Index position of the item
args - It is the optional arguments which if supplied, will be passed as third parameter to callback function.

Return:

It returns true when executed successfully.

Let's recreate our example:

Example:

<?php

$users = ['john', 'dave', 'tim'];

function print_item($item, $key)
{
	echo $item."\n";
}

array_walk($users, 'print_item');
?>

Output:

john
dave
tim

6. Array Iterator

This is quite advanced and complex way to iterate over an array. Honestly, I don't see the reason why you would need to use this over other methods, but for the purpose of fun & learning, let's explore this.

Here, we will create ArrayIterator object using ArrayObject function and use it to iterate over an array. It is based on pointer mechanism just like C++.

Example:

<?php

$users = ['john', 'dave', 'tim'];

$array_object = new ArrayObject($users);
$array_iterator = $array_object->getIterator();

while( $array_iterator->valid() )
{
    echo $array_iterator->current() . "\n";
    $array_iterator->next();
}
?>

Output:

john
dave
tim

Conclusion

We saw 6 ways to loop over an array in PHP so far. Personally, I like to use foreach because it is very simple but you can use any of the above method. Hope, this helped.

Happy Coding,

Adios.