PHP loop is a programming structure that allows you to repeatedly execute a block of code as long as a certain condition is true. 

There are several types of loops in PHP.

  1. While loop
  2. Do-while  loop
  3. For loop
  4. Foreach loop

1.   While loop:

The while loop is used when you want to execute the code as long as a condition is true.

<?php
$i = 0;
while ($i < 5) {
    echo "Value Of i : $i <br>";
    $i++;
}
?>
  • Initialization Expression ($i = 0): You initialize the variable before the loop.
  • Test Expression ($i < 5): The loop continues as long as this condition is true.
  • Update Expression ($i++): You update the variable inside the loop. 

Output:

Value Of i : 0
Value Of i : 1
Value Of i : 2
Value Of i : 3
Value Of i : 4  
 

2. Do-while loop:

 loops through a block of code once, and then repeats the loop as long as the specified condition is true

<?php
$i = 0;
do {
    echo "Value of i : $i <br>";
    $i++;
} while ($i < 5);
?>

Output:

Value Of i : 0
Value Of i : 1
Value Of i : 2
Value Of i : 3
Value Of i : 4

The block of code is executed once, and then the condition is checked.

3.  For loop:

The for loop is used when you know the number of iterations beforehand.

<?php
for ($i = 0; $i < 5; $i++) {
    echo "Value of i : $i <br>";
}
?>
  • Initialization ($i = 0): The loop starts by initializing a variable ($i in this case).
  • Condition ($i < 5): The loop continues as long as this condition is true.
  • Update ($i++): After each iteration, the variable is updated. $i++ is a shorthand for $i = $i + 1.  

Output:

Value Of i : 0
Value Of i : 1
Value Of i : 2
Value Of i : 3
Value Of i : 4
 

4. Foreach Loop:

Used for iterating over arrays or other iterable objects.

<?php
$colors = array("red", "green", "blue");
foreach ($colors as $color) {
    echo "Color: $color <br>";
}
?>

Output:

Color: red
Color: green
Color: blue