PHP Loops

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Different Types of Loops in PHP

Loops are used to repeat the execution of a block of code based on a specified condition. They automate repetitive tasks in a program, saving time and effort. PHP supports four types of loops:

while — iterates through a block of code as long as a specified condition remains true.
do…while — executes a block of code once, then repeats it as long as a specified condition is true.
for — loops through a block of code a specified number of times.
foreach — iterates through each element in an array and executes a block of code for each element.

At the end of this chapter, you will learn how to iterate through array values using the foreach() loop, which is specifically designed for arrays.

PHP while Loop

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

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

For example, the following code initializes $i=1. The loop continues to execute as long as $i is less than or equal to 3. Each iteration increments $i by 1:

Example

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<?php
$i = 1;
while($i <= 3){
$i++;
echo "The number is " . $i . "<br>";
}
?>

PHP do…while Loop

The do-while loop is a variant of the while loop. It executes the block of code once before checking the condition at the end of each iteration. If the condition is true, the loop continues to execute.

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

For example, the following code initializes $i=1. It executes the code block, increments $i by 1, and prints the output. Then, it evaluates the condition to determine if the loop should continue running as long as $i is less than or equal to 3:

Example

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<?php
$i = 1;
do{
$i++;
echo "The number is " . $i . "<br>";
}
while($i <= 3);
?>

Difference Between while and do…while Loop

The while loop and do-while loop differ in an important way — in a while loop, the condition is checked at the beginning of each iteration. If the condition is false initially, the loop won't execute at all.

On the other hand, a do-while loop executes its block of code at least once before checking the condition at the end of each iteration. Even if the condition is false initially, the loop runs once.

PHP for Loop

The for loop repeats a block of code based on a specified condition. It's commonly used when you know in advance how many times you want to execute the block of code.

for(initialization; condition; increment){
// Code to be executed
}

The parameters of a for loop are interpreted as follows:

initialization — Initializes the loop counter and is executed once before the loop starts.
condition — Checked before each iteration. If true, the loop continues; if false, the loop ends.
increment — Updates the loop counter after each iteration.

For example, the following code initializes $i=1. The loop continues to execute as long as $i is less than or equal to 3. Each iteration increments $i by 1:

Example

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<?php
for($i=1; $i<=3; $i++){
echo "The number is " . $i . "<br>";
}
?>

PHP foreach Loop

The foreach loop is specifically designed for iterating over arrays in PHP.

foreach($array as $value){
// Code to be executed
}

For example, the following code demonstrates how to iterate through and print the values of a given array:

Example

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<?php
$colors = array("Red", "Green", "Blue");

// Loop through colors array
foreach($colors as $value){
echo $value . "<br>";
}
?>

There is another syntax variation of the foreach loop, which extends the basic usage.

foreach($array as $key => $value){
// Code to be executed
}

Example

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<?php
$superhero = array(
"name" => "Peter Parker",
"email" => "peterparker@mail.com",
"age" => 18
);

// Loop through superhero array
foreach($superhero as $key => $value){
echo $key . " : " . $value . "<br>";
}
?>

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