foreach()

mysql_query

Hello. This is very newbish, but I need to know the function of the 'foreach' command and how to use it. I have looked at the PHP manual, and I simply don't get it. Perhaps on of you will make it clearer for me. Thanks.

benwestgarth

foreach() is a loop which simply provides a very convenient way to iterate through the contents of an array. For example: It is particularly useful when you need to display the contents of an array or test each value in the array against some condition.

There are two basic ways to use it (from the PHP manual):

foreach ($arr as $value) {
    echo "Value: $value<br>\n";
}

This code simply takes the array $arr and iterates through it one element at a time and places that element in $value. In this particular code example it then echos $value to screen. $value is arbitrary and could just as easily have been $foo. (as long as you then echo $foo).

The other way is quite similar but also allows iterates through the keys you assigned your array. If you created a basic array, then these would just be 0, 1, 2, 3, 4 ... n.

foreach ($arr as $key => $value) {
    echo "Key: $key; Value: $value<br>\n";
}

This code iterates through the array $arr and echos each value for $key and $value.

foreach() loops are very easy to use and you may benefit from a couple of experiments. Just create a couple of arbitrary arrays and dive in.

HTH, Ben

mysql_query

Hello Ben. Thank you for that reply.

Can you go into more detail about keys. (I think) this is what I'm working with.

this is a snippet of a code:

echo '<form method="post">';  

echo '<input type="hidden" name="Id" value="', $row['id'], '"/>'; 
foreach($rates as $key=>$value) 
...

I understand everything up to the foreach() part and the "..." aperently means I have to put something after it. 😃

This is a form that has a hidden value of Id. $row is gotten from a previous script, that displays other fields in that row.

Info is helpful. Thanks.

benwestgarth

The $key part of the code refers to the array index of the corresponding $value.

So, let's assume I create an array called $buildings and set the index values to letters using the following code:

$buildings  = array("a"=>"house", "b"=>"hut", "c"=>"castle");

Now suppose I want to display the values in that array along with their corresponding indexes. I would do this thus:

foreach($buildings as $key=>$value){
    echo "Key is $key and Value is $value<br>\n";
}

The output would read like this:

Key is a and Value is house
Key is b and Value is hut
Key is c and Value is castle

The best way to learn this is probably to use this example, or some of the examples in the PHP manual as a guide and mess around with the code to see how it works.

Anyway, HTH.
Ben

ednark

benwestgarth gave a good explaination:

here is an exlaination that helped me understand.. sometime you have to hear the same thing in several different ways before it clicks...

you know what arrays are... arrays store things by numbers array[0]='a', array[1]='b'

0 and 1, they are called indexes, they are unimportant and only hold the order of the item in the array

someone decided that they wanted to use something more descriptive than 0 and one, they called this a hashtable or hash, it is an array that can use strings as well as numbers

array['name'] = 'ednark'
array['country'] = 'usa'

now 'name' and 'country' are called the 'keys' instead of 'indexes'

when you step through and array with foreach() you can ask to be given only the value of the array at each step

foreach ( $array as $value )
{ ... }
good if you are only using unimportant indexes, it will step through in order so you don't need the index

or you can ask for the 'key' and the 'value' at each step

foreach ( $array as $key=>$value )
{ ... }

this is important when you use a meaningful 'key' and you need to know what type of info $value is a 'name' or a 'country' (as in my example above)

mysql_query

Ok, thanks for the explanation so far.

Now, if I have a form where a user chooses out of 5 radio buttons and PHP interperts this as an array, what has to come after foreach() if I want to insert this into a MySQL database? Something like this?

$query = 'INSERT INTO evaluation (Id,oneof5radiobuttons) VALUES ('.$_POST['Id'].','.$_POST['oneof5radiobuttons'].')';

Or does there have to be something before it?

Thanks.

mysql_query

anyone?

(Sorry, I want to keep this at the top and keep it from getting prued)

ednark

please post your html form that you are using... are at least the relevent radio button part

mysql_query

No Problem, here:

<body>

<form method="POST" action="ratingsystem.php">
  <input type="radio" value="a" checked name="oneof5radiobuttons">Excellent&nbsp;
  <input type="radio" name="oneof5radiobuttons" value="2">Good&nbsp;
  <input type="radio" name="oneof5radiobuttons" value="3">OK&nbsp;
  <input type="radio" name="oneof5radiobuttons" value="4">Not-so-good&nbsp;
  <input type="radio" name="oneof5radiobuttons" value="5">Sucks</p>
  <p><input type="submit" value="Submit" name="B1"></p>
</form>

</body>

ednark

try this, it should help you figure things out

<?php

print "<pre>";
print_r($HTTP_POST_VARS);
print "</pre>";

?>

<form method="POST" action="./">
  <input type="radio" name="oneof5radiobuttons" value="a" checked>Excellent&nbsp;
  <input type="radio" name="oneof5radiobuttons" value="2">Good&nbsp;
  <input type="radio" name="oneof5radiobuttons" value="3">OK&nbsp;
  <input type="radio" name="oneof5radiobuttons" value="4">Not-so-good&nbsp;
  <input type="radio" name="oneof5radiobuttons" value="5">Sucks</p>
  <p><input type="submit" value="Submit" name="B1"></p>

</form>

mysql_query

Ummm, that code doesn't work.

I made a very simple submission code for the above HTML form. Once again, her's the form:

<body>

<form method="POST" action="ratingsystem.php">
  <input type="radio" value="a" checked name="rating">Excellent&nbsp;
  <input type="radio" name="rating" value="2">Good&nbsp;
  <input type="radio" name="rating" value="3">OK&nbsp;
  <input type="radio" name="rating" value="4">Not-so-good&nbsp;
  <input type="radio" name="rating" value="5">Sucks</p>
  <p><input type="submit" value="Submit" name="B1"></p>
</form>

and here's ratingsystem.php

<?php
foreach($rating as $key=>$value) {
$query = 'INSERT INTO evaluation (rating) VALUES ('.$_POST['rating'].')';
}
echo "operation successful";
?>

This tells me that there's an "invalid argument for the 'foreach' statemnt". Can someone tell me why?

benwestgarth

Okay, I think I see where you are going wrong. $rating is NOT an array. It is a just a straight forward variable. That's how radio buttons work - you can only check one at a time so there is no need to for an array to hold a range of variables.

As such, foreach() is not what you want. Just insert $rating into your database using a normal mysql query statement. There is no need to loop through any values because there will be only one. From your code example that value will be either:

a,2,3,4 or 5

HTH, Ben

ednark

yes : $ratings is not an array it is a variable

thats what i was trying to get at with my example.

and the reason my code did not work is that i assumed the file was named index.php so you could just change
action="./" to action="thispage.php"