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
}
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<?php #loops.php // start, condition, increment for( $i=1; $i<=10; $i++ ) { //display this message echo "<p>". $i . ": shahid</p>"; } ?> |
An example script that uses for to print out the 7 times table:
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>The 7 Times Table</title> <link rel="stylesheet" type="text/css" href="/~cs1spw/tutorials/blue.css"> </head> <body> <h1>The 7 Times Table</h1> <ul> <?php for ($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)
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<?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:
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<?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”;
}
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<?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”;
}
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<?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.