Variable usage - how loose is it?

cable_guy_67 · #1 28-Jul-2005, 17:26

Hello All,

I have recently started dabbling in PHP and it seems that variables can be used/declared in quite a hodge podge manner. Perhaps I am missing something but why does this piece of code even work?

testing.php

PHP Code:


<?php
  if( $_POST ){
  $number_sent = count( $_POST );
  $my_message = $number_sent;
#  $my_array[$number_sent];
  do{
    $my_array[$i] = current($_POST);
    next($_POST);
    echo $my_array[$i];
    echo "<br>";
  }while(current($_POST));
  
  echo $my_array[0];
  echo "<br>";
  echo $my_array[1];
  echo "<br>";
  }
  else{
    $my_message = 'error';
  }
?>



<html>
<body>
</body>
  <form name="newform" method="post" action="index.html">
    <p>Message
      <input name="message" type="text" value="<?php echo $my_message; ?>" size=40 maxlength="400" />
    </p>
      <input type="submit" name="goback_but" value="Go Back" />
    </p>
  </form>
</html>

Before after actually indexing into $my_array I make no mention of it. Yet it works as anticipated otherwise. I origonally thought that I would have to use the $number_sent variable to declare $my_array but this does not seem to be the case. Am I to assume that I can just keep indexing the array at will? Scoping seems to be correct (there is no output outside the do ... while construct) but there does not seem to be an adverse effect to attempting to read into a non-existant array (outside the do ... while).

Coming from C++ to this seems, well, a little confusing.

Any thoughts on the matter would be most welcome.

Mark

Oh, the form that I come from has two named <input>'s of type text and a submit button (that is unnamed) giving me a value of 2 for number sent. I had played with both a for and do while getting to this point. That's why the array indexing outside the loop looks for [0] and [1].

Output:

Code:

Hello World        // from the loop
Goodbye World      //  from the loop
                   // outside the loop from last <br> in the loop
                   // outside the loop  last <br> moves Message down
Message  (text box shows '2' for the named <input>'s)

Code from index.html

HTML Code:


    <form action="testing.php" method="post">
      <p>
      Test 1 :
      <input name="test1" />
      Test 2 :
      <input name="test2" />
      <input type="submit" value="Submit" >
      </p>

    </form>

One last thing. The reason for the sparseness of the tags is I have been playing with the form class from the code section and have been testing default behavior against the documentation I have. Most likely not safe in a global sense but I like to see how things work by pushing on them (you know, with a hammer

) to see what happens.

JdS · #2 28-Jul-2005, 17:40

Quote:

Originally Posted by cable_guy_67

..I origonally thought that I would have to use the $number_sent variable to declare $my_array but this does not seem to be the case. Am I to assume that I can just keep indexing the array at will?...

Yes

Quote:

Originally Posted by cable_guy_67

...Scoping seems to be correct (there is no output outside the do ... while construct) but there does not seem to be an adverse effect to attempting to read into a non-existant array (outside the do ... while).

Try adding this line to the top of your script:

PHP Code:


<?php
error_reporting( E_ALL );
// your supplied code...
?>

cable_guy_67 · #3 28-Jul-2005, 17:50

Quote:

Originally Posted by JdS

Yes

Try adding this line to the top of your script:

PHP Code:


<?php
error_reporting( E_ALL );
// your supplied code...
?>

THANK YOU!
Now I get something more like I anticipated,

Code:

Notice: Undefined variable: i in C:\mytest\testing.php on line 10

Notice: Undefined variable: i in C:\mytest\testing.php on line 12
Hello

Notice: Undefined variable: i in C:\mytest\testing.php on line 10

Notice: Undefined variable: i in C:\mytest\testing.php on line 12
World

Notice: Undefined offset: 0 in C:\mytest\testing.php on line 16


Notice: Undefined offset: 1 in C:\mytest\testing.php on line 18

That's more like it. Seems to be more like -Wall in g++ would give me. Just because I can get away with something surely doesn't mean I should.

Mark

JdS · #4 28-Jul-2005, 17:53

Quote:

Originally Posted by cable_guy_67

...Just because I can get away with something surely doesn't mean I should...

EXACTLY... don't lose your good habits now. I always "define" my variables before using them, at least most of the time

cable_guy_67 · #5 28-Jul-2005, 19:18

I was just looking this code over and I realized when I pulled the for...

PHP Code:


#  for($i = 0; $i < $number_sent; $i++){

out, I never dealt with incrementing $i. Lord have Mercy, I will definately be using the error reporting from now on.

Mark

cable_guy_67 · #6 29-Jul-2005, 16:23

Well, after another day of fighting with types (or actually lack thereof) it seems that there is just no good way to make a variable act like I would like them to. I had high hopes with settype() but that still will promote an int to a float for something like,

Code:

$DefPercent + (((100 - $DefPercent) / $OtherIDs) * $OtherIDs )

The variables all get passed as arguments and I tried to con them into acting like integers to no avail. The division promotes to a float and messes up my integer math.

The only solution I can come up with is,

PHP Code:


$DefPercent + ((int)((100 - $DefPercent) / $OtherIDs) * $OtherIDs )

What a drag.

Mark

JdS · #7 29-Jul-2005, 18:25

You might also find floor() and similar functions useful in situations like this.

cable_guy_67 · #8 29-Jul-2005, 19:22

Quote:

Originally Posted by JdS

You might also find floor() and similar functions useful in situations like this.

My problem is just the extreme flexiblity of it all. I like integer math for things like this. floor() will still promote to a float.

Quote:

Originally Posted by PHP manual

Returns the next lowest integer value by rounding down value if necessary. The return value of floor() is still of type float because the value range of float is usually bigger than that of integer.

It would be nice if the language allowed for proper declaration of variables. Doing it with a cast like I did effectively does do what I want. Just something I am going to have to keep my eye on.

Dratted C++ getting me used to being specific. I was just getting to the point that I used constants and unsigned as a mechanism to keep numbers in check and not using globals (or very, very rarely). PHP's constants are all global in scope. I guess it has as much to do with the way the language is used though.

Thanks for the tip J.

Mark

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