Php while select array

6 ways to loop through an array in php

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

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.

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).

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.

 $users = ['john', 'dave', 'tim']; $i = 0; while($i  count($users))  echo $users[$i]."\n"; $i++; > ?>

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.

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.

 $users = ['john', 'dave', 'tim']; $i = 0; do  echo $users[$i]."\n"; $i++; > while($i  count($users)); ?>

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.

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 😉

 $users = ['john', 'dave', 'tim']; for($i = 0;$i  count($users);$i++) echo $users[$i]."\n"; ?> 

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.

//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.

 $users = ['john', 'dave', 'tim']; foreach($users as $user) echo $user."\n"; ?>

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».

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

• 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.

It returns true when executed successfully.

Let’s recreate our example:

 $users = ['john', 'dave', 'tim']; function print_item($item, $key)  echo $item."\n"; > array_walk($users, 'print_item'); ?>

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++.

 $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(); > ?>

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.

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Использование циклов в PHP

PHP имеет четыре вида циклов и операторы управления ими, рассмотрим поподробнее.

Foreach – перебор массива

Предназначен для перебора элементов массива.

$array = array( 1 => 'Значение 1', 2 => 'Значение 2', 3 => 'Значение 3', 4 => 'Значение 4', ); // Вывод ключей foreach ($array as $key => $val) < echo $key . '
'; > // Вывод значений foreach ($array as $key => $val) < echo $val . '
'; > 

Результат:

1 2 3 4 Значение 1 Значение 2 Значение 3 Значение 4

Альтернативный синтаксис foreach

For – цикл с счетчиком

Цикл работает пока выполняется заданное условие. Обычно применяется в качестве счетчика.

// Счетчик от 0 до 5 for ($n = 0; $n // Счетчик от 5 до 0 for ($n = 5; $n >= 0; $n--)

Результат:

Альтернативный синтаксис

$array = array( 'Значение 1', 'Значение 2', 'Значение 3', 'Значение 4', ); for ($n = 0; $n < count($array); $n++) < echo $array[$n] . '
'; >

Результат:

Значение 1 Значение 2 Значение 3 Значение 4

Альтернативный синтаксис for

While – цикл с предусловием

Т.е. если перед началом итерации условие выполняется, то цикл продолжает свою работу.

Результат:

Альтернативный синтаксис while

Do-while – цикл с постусловием

В отличии от while этот цикл проверяет выполнения условия после каждой итерации. Do-while не имеет альтернативного синтаксиса.

Результат:

Управление циклами

Break

Вызов break или break 1 в цикле останавливает его.

Для вложенных циклов используется break 2 и т.д.

Continue

Используется для пропуска итерации.

Результат:

Для вложенных циклов по аналогии с break 2 , break 3 – continue 2 , continue 3 .

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PHP Loops

In this tutorial you will learn how to repeat a series of actions using loops in PHP.

Different Types of Loops in PHP

Loops are used to execute the same block of code again and again, as long as a certain condition is met. The basic idea behind a loop is to automate the repetitive tasks within a program to save the time and effort. PHP supports four different types of loops.

• while — loops through a block of code as long as the condition specified evaluates to true.
• do…while — the block of code executed once and then condition is evaluated. If the condition is true the statement is repeated as long as the specified condition is true.
• for — loops through a block of code until the counter reaches a specified number.
• foreach — loops through a block of code for each element in an array.

You will also learn how to loop through the values of array using foreach() loop at the end of this chapter. The foreach() loop work specifically with arrays.

PHP while Loop

The while statement will loops through a block of code as long as the condition specified in the while statement evaluate to true.

The example below define a loop that starts with $i=1 . The loop will continue to run as long as $i is less than or equal to 3. The $i will increase by 1 each time the loop runs:

Example

PHP do…while Loop

The do-while loop is a variant of while loop, which evaluates the condition at the end of each loop iteration. With a do-while loop the block of code executed once, and then the condition is evaluated, if the condition is true, the statement is repeated as long as the specified condition evaluated to is true.

The following example define a loop that starts with $i=1 . It will then increase $i with 1, and print the output. Then the condition is evaluated, and the loop will continue to run as long as $i is less than, or equal to 3.

Example

Difference Between while and do…while Loop

The while loop differs from the do-while loop in one important way — with a while loop, the condition to be evaluated is tested at the beginning of each loop iteration, so if the conditional expression evaluates to false, the loop will never be executed.

With a do-while loop, on the other hand, the loop will always be executed once, even if the conditional expression is false, because the condition is evaluated at the end of the loop iteration rather than the beginning.

PHP for Loop

The for loop repeats a block of code as long as a certain condition is met. It is typically used to execute a block of code for certain number of times.

The parameters of for loop have following meanings:

• initialization — it is used to initialize the counter variables, and evaluated once unconditionally before the first execution of the body of the loop.
• condition — in the beginning of each iteration, condition is evaluated. If it evaluates to true , the loop continues and the nested statements are executed. If it evaluates to false , the execution of the loop ends.
• increment — it updates the loop counter with a new value. It is evaluate at the end of each iteration.

The example below defines a loop that starts with $i=1 . The loop will continued until $i is less than, or equal to 3. The variable $i will increase by 1 each time the loop runs:

Example

PHP foreach Loop

The foreach loop is used to iterate over arrays.

The following example demonstrates a loop that will print the values of the given array:

Example

There is one more syntax of foreach loop, which is extension of the first.

Example

 "Peter Parker", "email" => "peterparker@mail.com", "age" => 18 ); // Loop through superhero array foreach($superhero as $key => $value)< echo $key . " : " . $value . "
"; > ?>

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