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Languages :: PHP :: PHP and data structures
By: progGoon U.S.A.  Date: 22/03/2003 00:00:00  English  Points: 500 Status: Answered
Quality : Excellent
I am setting out to learn PHP, I come from a heavy C background and I would like to use some simple data structures, but I do not have the slightest clue how to set this up in PHP

here is what I am talking about(in C of course)

struct foo
{
char *name;
char *output;
}

// disregard the non-allocation of strings, just example

foo fooArray =
{{"one", "first"},
{"two", "second"}};

yadda yadda yadda

then how do I access these in the array

if(strstr(fooArray[0].name, CONTANT_ONE) == 0)
{
}

I need to setup some data structures similar to that above and I am just stuck at where to start. Do I have to use the array functions to put this into the structure and also to access the members?

Sorry if this is a stupid question, I am new to this whole "compile/interpret" on the fly scripting language. Just seems odd.
By: TheFalklands Date: 23/03/2003 07:09:00 English  Type : Comment
Hi,

Welcome to PHP coding.

Now you need no struct etc. here. You can use arrays to do what you intend to do :)

like this :

$foo_array=array("key1"=>"value1","key2"=>"value2");

so you can access it as $foo_array["key1"]

Please see the PHP manual for using arrays in diff. ways.

Enjoy PHP!

Cheers,
By: sumotimor Date: 23/03/2003 07:15:00 English  Type : Comment
TheFalklands,

So if I want a "contsant" array, can I put that in my constants.php file and just include it and I will be able to access it?

Wow....quite a bit easier and quicker without having to worry about all the memory management in C.

Thanks,
sumotimor
By: VGR Date: 23/03/2003 07:19:00 English  Type : Answer
structs are records
PHP doesn't have records.
This has to be implemented as an Object IMHO)

<A HREF="http://www.php.net/manual/en/language.types.php">http://www.php.net/manual/en/language.types.php</a>

and arrays are a basic structure. You don't have to allocate nor dispose the variables, they are garbage-collected at the end of execution of the script (except for explicitly-set SESSION data)

your foo array would be declared, allocated and filled-in all in one statement (like in BASIC) by :
$fooArray=array(0=>array(0=>'one',1=>'two'),1=>array(0=>'two',1=>'second'));

(it's good common practice to first declare&empty the variable as an array, though : $fooArray=array(); )
This is because arrays are associative in PHP ($key => $value) pairs. Also, all variables are POLYMORHPIC. Usually (except for floating-point or type-forced operations), you never have to typecast.

Personally, I would declare $fooArray differently for the same achieved result :
$fooArray=array();
$fooArray[0]=array(0=>'one',1=>'two');
$fooArray[1]=array(0=>'two',1=>'second');

As for strstr(), this function exists in PHP and mimicks the C one, so you shouldn't have any problem.
Constants do exist also, define()-ed

Arrays are open arrays (no limit nor size specified).

This will show you the power of PHP arrays/vectors :
(<A HREF="http://www.php.net/manual/en/language.types.array.php">http://www.php.net/manual/en/language.types.array.php</a>)

<?php
$arr = array(5 => 1, 12 => 2);

$arr[] = 56; // This is the same as $arr[13] = 56;
// at this point of the script

$arr["x"] = 42; // This adds a new element to
// the array with key "x"

unset($arr[5]); // This removes the element from the array

unset($arr); // This deletes the whole array
?>

<?php
// this
$a = array( 'color' => 'red',
'taste' => 'sweet',
'shape' => 'round',
'name' => 'apple',
4 // key will be 0
);

// is completely equivalent with
$a['color'] = 'red';
$a['taste'] = 'sweet';
$a['shape'] = 'round';
$a['name'] = 'apple';
$a[] = 4; // key will be 0

$b[] = 'a';
$b[] = 'b';
$b[] = 'c';
// will result in the array array(0 => 'a' , 1 => 'b' , 2 => 'c'),
// or simply array('a', 'b', 'c')
?>

<?php
$colors = array('red', 'blue', 'green', 'yellow');

foreach ($colors as $color) {
echo "Do you like $color?\n";
}

/* output:
Do you like red?
Do you like blue?
Do you like green?
Do you like yellow?
*/
?>
<?php
foreach ($colors as $key => $color) {
// won't work:
//$color = strtoupper($color);

// works:
$colors[$key] = strtoupper($color);
}
print_r($colors);

/* output:
Array
(
[0] => RED
[1] => BLUE
[2] => GREEN
[3] => YELLOW
)
*/
?>
arrays may be parsed by keys through
foreach($fooArray as $key=>$value) {
// play with $key and its $value
} // foreach
or via indices
for ($i=0;$i<count($fooArray);$i++) {
// play with $fooArray[$i]["key"] and $fooArray[$i]["value"]
// or just the value with $fooArray[$i] if you used a pure-numeric filling-in like $fooArray[0]=1; $fooArray[1]=2; etc
} // for


Finally, PHP is not compiled at all (unless you use some semi-compiler like ZEND) but runs very fast, compared to other scripting languages (VBScript for ASP, etc)

If you write about accessing "members" of data structures, I think you definitely enter the field of the "object" type in PHP ;-)

Regards,
By: TheFalklands Date: 23/03/2003 07:26:00 English  Type : Comment
Hi,

>> So if I want a "contsant" array, can I put that in my constants.php file and just include it and I will be able to access it?

Yes, you can access it. In functions you need to declare it as global.

I hope the answer from VGR is very good explanation.

Enjoy!

Cheers,
By: VGR Date: 23/03/2003 20:07:00 English  Type : Comment
I think I remember there is no GLOBAL declaration needed for constants.
By: TheFalklands Date: 23/03/2003 23:28:00 English  Type : Comment
Frankly! I had not defined an array as constants(I don't think it can be!).

How do you think array is defined as constant? Using define()? Will it work?

Thanks
By: VGR Date: 24/03/2003 00:07:00 English  Type : Comment
no, I don't think an array, even hardcoded, can be put in a define statement to become a constant. But this should be tried right out 8-)

I was just stating that IMHO, inside the scope of a function, the GLOBAL keyword is not needed to access constants defined globally. So constants and $_SESSION[] are truely global. The rest are "under-globals"
By: progGoon Date: 24/03/2003 00:50:00 English  Type : Comment
VGR,

(nothing has been tested, still trying to setup stuff and understand this new found joy of scripting =)).

ok last question(well maybe), I have this so far

$FORM_ARRAY[5] = array(0 => 'Ttl', 1 => 'Defaults', 2 => 'Title');
$FORM_ARRAY[6] = array(0 => 'BGImage', 1 => 'Defaults', 2 => 'Background Image');

now can I do the following
foreach($_POST as $formIndex)
{
// This is were I am stuck
// writeIni($section, $key, $value)
// first iteration $formIndex = 'Title' right?
writeIni($FORM_ARRAY[$formIndex][0], //should be 'Ttl'
$FORM_ARRAY[$formIndex][1], //should be 'Title'
// lost here, not too sure about $_POST data
// I need to output the value in the form
$formIndex);
}

I am not understanding how to access a multi-dimensional array in this.

I hope this makes it a bit more clear what I am trying to do. Main task is to process an entire forms page in one loop.

if you want to email me, feel free, we can discuss it via email and I will 'echo' it back up here for record purposes
awscrib at earthlink dot net(please let me know if off board discussion are discouraged now, I have not been here in awhile).
By: progGoon Date: 24/03/2003 00:52:00 English  Type : Comment
ugh.....edit....sorry

// first iteration $formIndex = 'Title' right?
writeIni($FORM_ARRAY[$formIndex][1], //should be 'Defaults'
$FORM_ARRAY[$formIndex][2], //should be 'Title'
By: progGoon Date: 24/03/2003 00:54:00 English  Type : Comment
VGR,

sorry, just noticed the link you sent from php.net that pretty much describes what I am trying to do, I will let you know, but I think this page will work for refernce

Thank you very much!

-

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