1. Introduction
In this article in the series, we are learning about different types of loops. Loops are programming constructs that can be used to repeat a particular task, or in other words, we can say loops are used to execute the same block of code again and again by some pre-defined conditions. The primary use of loop is to automate repetitive tasks and save time and efforts.
In PHP, we have the following types of loops:
- while: loops through a block of code until the condition evaluates to true.
- do…while: The block of code executes once, and then condition gets computed. If the condition results in a true, the statement is repeated as long as the specific 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.
Let us go through them to understand each loop deeply.
2. PHP while loop
The while loop executes the code block until the condition results in true. The syntax of while loop is:
while(condition){
// Code to be executed
}
The code below demonstrates the use of while loop which starts
$i = 1 with and keeps executing until the condition $i <= 5 results in true.$i = 1;
while($i <= 5){
$i++;
echo "Value of $i is " . $i . "<br>";
}
Output:
Value of $i is 1 Value of $i is 2 Value of $i is 3 Value of $i is 4 Value of $i is 5
3. PHP do-while loop
The do-while loop is a modified version of while loop. The while loop evaluates the condition at the starting of iteration, but the do while evaluates the condition at the end of every iteration, after execting it once.
The do-while loop always executes the loop once and keeps iterating until the condition results in true. The syntax of do-while is:
do{
// Code to be executed
}while(condition);
The code below demonstrates the use of do-while loop which starts with $i = 1 and keeps executing until the condition $i <= 5 results in true.
$i = 1;
do{
$i++;
echo "Value of $i is " . $i . "<br>";
}while($i <= 5);
Output:
Value of $i is 1 Value of $i is 2 Value of $i is 3 Value of $i is 4 Value of $i is 5
4. PHP for loop
The for loop is the most frequently used loop. It repeats a block of code until a certain condition is true. The syntax of for loop is:
for(initialization; condition; increment){
// Code to be executed
}
Let’s discuss the three parameters of for loop:
- initialization — used to initialize the counter variables and evaluated once unconditionally before the first execution of the body of the loop.
- condition — at the beginning of each iteration, the condition gets computed. If the condition results in true, the loop continues, and the statements in the block are executed, else the execution of the loop ends.
- increment — increment updates the loop counter. It is evaluated at the end of each loop iteration.
Consider:
for($i=1; $i<=5; $i++){
echo "Value of $i is " . $i . "<br>";
}
The output of the above code would be:
Value of $i is 1 Value of $i is 2 Value of $i is 3 Value of $i is 4 Value of $i is 5
5. PHP foreach loop
The foreach loop is mostly used to iterate over arrays. The syntax is:
foreach($array as $value){
// Code to be executed
}
The following example demonstrates the use of foreach loop that will print the values of the given array:
$planets = array("Earth", "Mars", "Venus");
// Loop through $plants array
foreach($planet as $planet){
echo $planet . "<br>";
}
The output would be:
Earth Mars Venus
There is one more syntax of the foreach loop, which is an extension of the above syntax.
foreach($array as $key => $value){
// Code to be executed
}
The
$key contains the key of the array. So, the above example becomes –$planets = array("Earth", "Mars", "Venus");
// Loop through $plants array
foreach($planet as $key => $planet){
echo $planet . " is at position ". $key ."<br>";
}
The output would be:
Earth is at position 0 Mars is at position 1 Venus is at position 2
6. Conclusion
In this article, we had an in-depth look at different types of looping constructs and how and where we can use them. In the next article of this series, we will learn about different HTTP related capabilities of PHP programming language. Till then, try printing table of 2 using for loop.