Loops in PHP

To avoid repeating the same code snippets multiple times, loops are used. So, how many kinds of loops are there in PHP, and how are they used? Let's explore right away.

I. Why Use PHP Loops

When you write code with many repetitive sections, you can't simply copy and paste the same line or block of code multiple times because it can easily lead to syntax errors and is very time-consuming. For this reason, most programming languages have loop features to help you solve this problem.

In PHP, there are the following types of loops:

• while - the loop continues to run as long as the condition is true.
• do ... while - a variant of the while loop, which checks the condition at the end of each iteration.
• for - loop through a block of code a specified number of times.
• foreach - loop through a block of code for each element in an array.

II. While Loop

The loop continues to run as long as its condition is true.

1. Syntax

while (condition is true){
 the code is executed;
}

2. Example

Here is an example: Print numbers from 1 to 10.

$x = 1;
while($x <= 10) {
 echo "This is the number: $x <br>";
 $x++;
}

While running the code above, it will check the condition. If the condition is true, the code will execute. Then it will check the condition again, and if still true, execute the code again. This continues until the condition is false. In other words, it checks the condition first before running the code. The variable $x is increased by 1 after each iteration, and when $x equals 11, the condition is no longer true, and the while loop ends.

III. Do ... While Loop

The do ... while loop is a variant of the while loop that checks the condition at the end of each loop iteration.

1. Syntax

do {
 code will execute
} while (condition is true);

2. Example

Here is an example: Print numbers from 1 to 10.

$x = 1;
do {
 echo "This is the number: $x <br>";
 $x++;
} while ($x <= 10);

The loop starts with $x = 1, then it prints the output and increments $x by one. Next, it is evaluated by the condition, and the loop will continue as long as $x is less than or equal to 10.

IV. For Loop

The for loop is used when you know how many times a block of instructions will run in advance.

1. Syntax

for (init counter; test counter; increment counter) {
  execute code;
}
Explanation:
 + init counter: Initialize the loop counter value
 + test counter: Check the condition. If it is TRUE, the loop continues. If it is FALSE, the loop ends.
 + increment counter: Increase the loop counter value.

2. Example

Here's an example: Print numbers from 1 to 10.

for ($x = 1; $x <= 10; $x++) {
 echo "This is the number: $x <br>";
}

The loop starts with $x = 1, and continues until $x = 11, at which point it will stop. $x is incremented after each iteration.

V. Foreach Loop

The foreach loop is used to iterate over arrays.

1. Syntax

foreach ($array as $value) {
 executable code;
}

2. Example

Here's an example: Print each element in the array $array = ["a", "b", "c", "d"].

$array = ["a","b","c","d"];
foreach ($array as $item {
 echo "Element : " . $item . "\n";
}

To get the keys' values of each element in the array, use the following extended syntax.

foreach ($array as $key => $value) {
 executable code;
}

VI. Break and Continue Keywords

1. Break Keyword

The break keyword is used to terminate the execution of a loop prematurely.

Example: Print numbers from 1 to 10. Exit the loop when it reaches the number 4.

for ($x = 1; $x <= 10; $x++) {
 if ($x == 4) {
 break;
 }
 echo "This is the number: $x <br>";
}

2. Continue Keyword

The continue keyword is used to skip the current iteration without stopping the whole loop like break.

Example: Print numbers from 1 to 10. Do not print the number 4.

for ($x = 1; $x <= 10; $x++) {
  if ($x == 4) {
    continue;
  }
  echo "This is number: $x <br>";
}

In conclusion, the continue keyword is similar to break, but it only ends the current iteration early, not the entire loop.