=> Operator

[mcloan]

I am in the process of learning php.  In the book I am reading it has an array as $prices = array('tires=>'100', 'oil'=>10);

Can someone tell me what the => means?  Is this different than just =

Thank you.

[wildteen88]

=> sets the key for an item in an array.

For example the following code:
[code=php:0]$prices = array('tires=>'100', 'oil'=>10);[/code]

Sets up a variable called prices which stores an array which has two items

tires and oil

the string to the left of => operator setups up the key. The stuff after the => operators sets the value for the key.

The key is what you use in the square brakets, eg:
$prices['tires'] $proces['oil']

So tires holds the value of 100 and oil holds the value of 10

If you didnt have the => operator PHP will use a numeric key instead starting at zero for the first item, 1 for the secound, 2 for the third etc.

Hope that helps.

[mcloan]

Very helpful.

Thank you so much!

[obsidian]

in addition, it allows you to [b]pull[/b] the key out of an array when looping in a foreach. it has other more obscure functions as well, but i'll let someone a little more familiar with it cover those.
[code]
<?php
foreach ($myArray as $key => $val) {
  echo "$key = $val<br />\n";
}
?>
[/code]

[mcloan]

[quote author=obsidian link=topic=112256.msg455582#msg455582 date=1161463474]
in addition, it allows you to [b]pull[/b] the key out of an array when looping in a foreach. it has other more obscure functions as well, but i'll let someone a little more familiar with it cover those.
[code]
<?php
foreach ($myArray as $key => $val) {
  echo "$key = $val<br />\n";
}
?>
[/code]
[/quote]

Thank you actually this use is what invoked my question, but I am still a little confused on this application of it.  For instance.  You may invoke the above code by setting it up as a function and passing $myArray as a variable which will probably be $_Post.

So if the above was function was named fillout, it would do something like the below:

fillout($_Post)

function fillout($myArray)
{
foreach ($myArray as $key => $val) {
  if (!isset($key) || ($val== ' '))
      return false;
}
      return true;
}

What I do not understand is how the value ($val) is getting set?  The key will be the form name but what about the value?  I think it may be in $_Post but I do not have a clear understanding of exactly what $_Post does.  It is setting up an associtive array with $key as field name => value of field name for each field on a form?

Your help is much appreciated.

Thank you.

[obsidian]

OK, as you stated, $_POST is an associative array. An associative array is an array made up of keys for the placeholders and values (what is stored at each key location). So, if I were to create an associative array, I would do the following:
[code]
<?php
$array = array(
  'key1' => 'value1',
  'key2' => 'value2',
  'key3' => 'value3
);
?>
[/code]

Now, if I were wanting to use the foreach() like I showed above on this array I just created, it would simply return all the keys and values of the array:
[code]
<?php
foreach ($array as $key => $val) {
  echo "$key is $val<br />\n";
}

// ouputs:
// key1 is value1
// key2 is value2
// key3 is value3
?>
[/code]

Once you have that understanding, you can apply it to the $_POST array knowing that the [b]keys[/b] of the post array are the [b]names[/b] of your form fields and the [b]values[/b] of the array are the [b]values[/b] of your form fields. So, if you were simply checking to make sure that your name and email address fields were not left empty, you could use the following:
[code]
<?php
foreach ($_POST as $key => $val) {
  if (($key == 'name' || $key == 'email') && empty($val)) {
    // either the name or the email address field is empty!
  }
}
?>
[/code]

On a side note, you really never need to use isset() on the keys when you are looping through the $_POST variable. Since foreach() only cycles through those variables that are in the array, every key returned is set already.

Does this help some?

[mcloan]

obsidian -

Perfect, your example is exactly what I needed to understand.  I really appreciate the thorough example.  Now I finally have the concept down. This will help me so much as I move forward in my book.

Thank you again!!!!

[obsidian]

[quote author=mcloan link=topic=112256.msg458590#msg458590 date=1161960595]
Perfect, your example is exactly what I needed to understand.  I really appreciate the thorough example.  Now I finally have the concept down. This will help me so much as I move forward in my book.
[/quote]

Excellent. That's what we're here for ;) ... Out of curiosity, what book are you working through?

[mcloan]

The book is php and msql web development by luke wellington and laura thomson.  It is a darn good book so far.