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Using Control Structures and Foreach Loops in PHP

By Darren W. Hedlund
2005-06-21

PHP Foreach Loops

The type of control structure we're going to discuss is the 'foreach' loop.� The 'foreach' loop allows you to iterate over each value of an array.� The 'foreach' loop has two syntaxes, one for arrays you might have initialized, and one more specifically for associated arrays which you might have initialized.� Here are the syntaxes for both:

foreach (array_expression as $value) { do something with $value }
foreach (array_expression as $key => $value) { do something with $key and $value }



$people = array(Darren,'Jeff','Joseph',Scott,'David','Alex');


As you can see, we've declared an array called $people which store the names of a few people.� While you can get access each element using $people[0 to 5] (as we discussed in our array lesson), if you didn't know how big the array was, you'd never know how far to go.� There is a combination of a loop and a function you could use, but for now, this is the SIMPLEST way to iterate through an entire array.� Let's use the above array and the above "foreach" loop syntax to write out a simple example:



$people = array(Darren,'Jeff','Joseph',Scott,'David','Alex');
foreach ($people as $person) { //note the singular and plural variable names
� echo "$person\n";
}


The above "foreach" loop says the following:� "foreach element (person) in the array (people), print the element (person's name)".� The example above will have the following output:

"Darren
Jeff
Joseph
Scott
David
Alex"

Of course you don't just have to print out each value in the array.� There are endless possibilities of what you can do with each value in the array.� I just think that printing each element is the easiest and therefore will show you the most clearly how to use a "foreach" loop.� Let's do the same thing with the associated array syntax:



$people = array('person1' => 'Darren','person2' => 'Jeff','person3' => 'Joseph','person4' => 'Scott','person5' => 'David','person6' => 'Alex');
foreach ($people as $person => $name) { //again note the singular and plural variables names
� echo "$person - $name\n";
}

The example above will have the following output:

"person1 - Darren
person2 - Jeff
person3 - Joseph
person4 - Scott
person5 - David
person6 - Alex"

That's about it for the "foreach" loop.� So you might ask why is the "foreach" loop called a control structure.� Well that's because PHP will run the block of code as many times as there are elements in the array.� It will execute the block, move back up, and execute again until all the elements are dealt with.

That's about it for the "foreach" loop.� Hopefully those of you reading the tutorials aren't finding these hard or complicated to understand.� The lessons at this point might seem a little like they're all over the place, but by the time the main lessons are complete, I'll demonstrate putting all these lessons together to create simple programs.� For those of you that really want to learn, expect homework after the main lessons are done.� The homework won't be at all complicated or tricky, but it will help you understand some of PHP's features better.




Tutorial pages:
  • PHP Foreach Loops

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