PHP Loops Tutorial

Loops are used in php to perform an action many times. For example, we want to display our name 100 times on a webpage. Instead of typing it 100 times, we can use a loop. The loop will display it 100 times.

PHP FOR LOOP

A FOR loop requires three parameters:

start: the starting point, a value for the counter variable
condition: the condition that has to be met to run the loop again
increment: the counter has to be incremented (or decremented) before the loop is run again

for(start; condition; increment )
{
// Code to repeat
}

<?php #loops.php
    //     start,  condition, increment 
     for(  $i=1;   $i<=10;    $i++     )
    {
         //display this message
         echo "<p>". $i . ": shahid</p>";
    }
?>

An example script that uses for to print out the 7 times table:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"> <html> 
   <head> 
      <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
      <title>The 7 Times Table</title> 
      <link rel="stylesheet" type="text/css" href="/~cs1spw/tutorials/blue.css"> 
   </head> 
   <body> 
      <h1>The 7 Times Table</h1> 
      <ul> 
      <?php 
          for ($i = 1; $i <= 10; $i++) 
          { 
            echo "<li>$i times 7 is ".($i * 7)."</li> "; 
          } 
      ?>
      </ul> 
    </body> 
</html>

PHP WHILE LOOP

A WHILE loop will run a piece of code again and again until the condition becomes false. The code will be repeated only while the condition is true.

For a while loop you will need:

initialisation expression to be evaluated just once before the loop (start)
test expression to be evaluated each time the loop runs (condition)
loop body: the block of code to be repeated
iteration expression to be run after each loop execution (increment)

Please Note: without an increment you will have an infinite loop: it will never stop on its own. (fortunately modern browsers are able to stop them)

<?php #loops.php
   //Start counting
   $count = 1;

   //loop condition
   while($count <= 10)
  {
     //display a message
     echo "<p>$count: this is a while loop</p>";

     //increment value of count by one
     $count++;
  } 
?>

PHP DO-WHILE LOOP

A DO-WHILE loop can be used to execute the body at least once (the very first time) and it will have this syntax:

do
{
statement
} while(condition)

Here a working sample:

<?php #loops.php
   //set the counter
   $count = 1;

   //do-while
   do
  {
     //display a message
     echo "<p>$count: this is a do-while loop</p>";

     //increment value of count by one
     $count++;
  } while($count <= 10)  //condition
?>

PHP For Each Loop

A FOREACH loop will allow you to iterate over elements in an array. You can use a foreach loop accessing each key of an array or both keys and values.

Accessing keys:

foreach ($array as $key){
echo “$key”;
}

<?php #loops.php
   //the array
   $colours = array("red", "green", "blue" );

   //foreach loop
   foreach($colours as $colour)
  {
     //display a message for each item
     echo "<p>$colour</p>";
  } 
?>

Accessing keys and values:

foreach ($array as $key => $value) {
echo “$key : $value”;
}

<?php #loops.php
   //an associative array
   $colours = array("red" => "#F00", 
                    "green" => "#0F0",
                    "blue" => "#00F"
 );

   //foreach loop
   foreach($colours as $colour => $code)
  {
     //accessing keys and values
     echo "<p>The hexadecimal code for <strong>$colour</strong> is: $code.</p>";
  } 
?>

Click here to read about PHP functions.

PHP FOR LOOP

A FOR loop requires three parameters:

start: the starting point, a value for the counter variable
condition: the condition that has to be met to run the loop again
increment: the counter has to be incremented (or decremented) before the loop is run again

for(start; condition; increment )
{
// Code to repeat
}

<?php #loops.php
    //     start,  condition, increment 
     for(  $i=1;   $i<=10;    $i++     )
    {
         //display this message
         echo "<p>". $i . ": shahid</p>";
    }
?>

<?php #loops.php

// start, condition, increment

for( $i=1; $i<=10; $i++ )

{

//display this message

echo "". $i . ": shahid";

}

An example script that uses for to print out the 7 times table:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"> <html> 
   <head> 
      <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
      <title>The 7 Times Table</title> 
      <link rel="stylesheet" type="text/css" href="/~cs1spw/tutorials/blue.css"> 
   </head> 
   <body> 
      <h1>The 7 Times Table</h1> 
      <ul> 
      <?php 
          for ($i = 1; $i <= 10; $i++) 
          { 
            echo "<li>$i times 7 is ".($i * 7)."</li> "; 
          } 
      ?>
      </ul> 
    </body> 
</html>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"> <html>

<head>

<title>The 7 Times Table</title>

</head>

<body>

<h1>The 7 Times Table</h1>

<ul>

<?php

for ($i = 1; $i <= 10; $i++)

{

echo "<li>$i times 7 is ".($i * 7)."</li> ";

}

</ul>

</body>

</html>

PHP WHILE LOOP

A WHILE loop will run a piece of code again and again until the condition becomes false. The code will be repeated only while the condition is true.

For a while loop you will need:

initialisation expression to be evaluated just once before the loop (start)
test expression to be evaluated each time the loop runs (condition)
loop body: the block of code to be repeated
iteration expression to be run after each loop execution (increment)

Please Note: without an increment you will have an infinite loop: it will never stop on its own. (fortunately modern browsers are able to stop them)

<?php #loops.php
   //Start counting
   $count = 1;

   //loop condition
   while($count <= 10)
  {
     //display a message
     echo "<p>$count: this is a while loop</p>";

 //increment value of count by one 
$count++; 
} 
?>

<?php #loops.php

//Start counting

$count = 1;

//loop condition

while($count <= 10)

{

//display a message

echo "$count: this is a while loop";

//increment value of count by one

$count++;

}

PHP DO-WHILE LOOP

A DO-WHILE loop can be used to execute the body at least once (the very first time) and it will have this syntax:

do
{
statement
} while(condition)

Here a working sample:

<?php #loops.php
   //set the counter
   $count = 1;

   //do-while
   do
  {
     //display a message
     echo "<p>$count: this is a do-while loop</p>";

 //increment value of count by one 
$count++; 
} 
while($count <= 10)  
//condition 
?>

<?php #loops.php

//set the counter

$count = 1;

//do-while

{

//display a message

echo "$count: this is a do-while loop";

//increment value of count by one

$count++;

}

while($count <= 10)

//condition

PHP For Each Loop

A FOREACH loop will allow you to iterate over elements in an array. You can use a foreach loop accessing each key of an array or both keys and values.

Accessing keys:

foreach ($array as $key){
echo “$key”;
}

<?php #loops.php
   //the array
   $colours = array("red", "green", "blue" );

   //foreach loop
   foreach($colours as $colour)
  {
     //display a message for each item
     echo "<p>$colour</p>";
  } 
?>

<?php #loops.php

//the array

$colours = array("red", "green", "blue" );

//foreach loop

foreach($colours as $colour)

{

//display a message for each item

echo "$colour";

}

Accessing keys and values:

foreach ($array as $key => $value) {
echo “$key : $value”;
}

<?php #loops.php
   //an associative array
   $colours = array("red" => "#F00", 
                    "green" => "#0F0",
                    "blue" => "#00F"
 );

   //foreach loop
   foreach($colours as $colour => $code)
  {
     //accessing keys and values
     echo "<p>The hexadecimal code for <strong>$colour</strong> is: $code.</p>";
  } 
?>

<?php #loops.php

//an associative array

$colours = array("red" => "#F00",

"green" => "#0F0",

"blue" => "#00F"

);

//foreach loop

foreach($colours as $colour => $code)

{

//accessing keys and values

echo "The hexadecimal code for $colour is: $code.";

}

Click here to read about PHP functions.