Loops

PHP Loops


Often when you write code, you want the same block of code to run over and over again a certain number of times. So, instead of adding several almost equal code-lines in a script, we can use loops.

Loops are used to execute the same block of code again and again, as long as a certain condition is true.

In PHP, we have the following loop types:

  • while – loops through a block of code as long as the specified condition is true
  • do...while – loops through a block of code once, and then repeats the loop as long as the specified condition is true
  • for – loops through a block of code a specified number of times
  • foreach – loops through a block of code for each element in an array

 


The PHP while Loop

 

The while loop executes a block of code as long as the specified condition is true.

Syntax

while (condition is true) {
  code to be executed;
}

Examples

The example below displays the numbers from 1 to 5:

Example

<?php
$x = 1;
while($x <= 5) {
echo “The number is: $x <br>”;
$x++;
}
?>

The PHP do…while Loop

The do...while loop will always execute the block of code once, it will then check the condition, and repeat the loop while the specified condition is true.

Syntax

do {
  code to be executed;
} while (condition is true);

Examples

The example below first sets a variable $x to 1 ($x = 1). Then, the do while loop will write some output, and then increment the variable $x with 1. Then the condition is checked (is $x less than, or equal to 5?), and the loop will continue to run as long as $x is less than, or equal to 5:

Example

<?php
$x = 1;
do {
echo “The number is: $x <br>”;
$x++;
} while ($x <= 5);
?>

The PHP for Loop

The for loop is used when you know in advance how many times the script should run.

Syntax

for (init counter; test counter; increment counter) {
code to be executed for each iteration;
}

Parameters:

  • init counter: Initialize the loop counter value
  • test counter: Evaluated for each loop iteration. If it evaluates to TRUE, the loop continues. If it evaluates to FALSE, the loop ends.
  • increment counter: Increases the loop counter value

Examples

The example below displays the numbers from 0 to 10:

Example

<?php
for ($x = 0; $x <= 10; $x++) {
echo “The number is: $x <br>”;
}
?>

The PHP foreach Loop

The foreach loop works only on arrays, and is used to loop through each key/value pair in an array.

Syntax

foreach ($array as $value) {
code to be executed;
}

For every loop iteration, the value of the current array element is assigned to $value and the array pointer is moved by one, until it reaches the last array element.

Examples

The following example will output the values of the given array ($colors):

Example

<?php
$colors = array(“red”, “green”, “blue”, “yellow”);
foreach ($colors as $value) {
echo “$value <br>”;
}
?>

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