http://pastebin.com/yxDrb5hR

Thanks guys. I will look into these and see what comes out well :)

First:

If your page is "not loading," that probably means you have error reporting disabled. You should enable error reporting during development so you don't have to guess at what's going wrong.

In your php.ini file, find these settings and comment them out (i.e., prepend them with a ; - do not delete them, you'll want to restore them when you're done with your debugging):

  ;error_reporting  =  {this might be any of several values}
  ;display_errors = Off
  ;display_startup_errors = Off

then give them these values:

  error_reporting  =  E_ALL
  display_errors = On
  display_startup_errors = On

Next, the obvious problem with your function is that $wares does not exist.

It's also very difficult to figure out what you're trying to do - your function seems to be very tightly related to the data structures you expect to receive. Can you show an example of what your arrays [are supposed to] look like?

still it doesn't load. Chrome states "HTTP 500 Internal Server Error."

some hosts are more zealous about hiding errors. Ask them about it. Also ask about where your error log file is; PHP errors should be being logged there.

$wares does exist, ...

Not in your function, it doesn't.

Read up about "scope" in PHP. Variable scope is, basically, the "space" within a script where variables "exist." Classes and functions in PHP have their own scope. Example:

  <?php

  $myvar = "some value";
  # this is the "global scope."
  # if you declare $myvar here, 
  #   it's available anywhere in the global scope.

  if( condition ){
      # conditional blocks, loops, etc. don't have their own scope
      # $myvar is available here.
  }

  function myfunc(){
      # functions *do* have their own scope - 
      # $myvar does not exist here!

      $myvar = "other value";
      # if you declare $myvar inside the function,
      #   it **is not** the same as the $myvar in the global scope.
      print $myvar;
      # local (myfunc) scope - prints "other value"
  }
  print $myvar;
  # global scope - prints "some value"

To use a global variable inside a function, you need to either pass it in (preferred), or import it from the global scope.

  <?php

  # pass the variable you need into the function
  ## preferred ##
  function pass( $arg ){
      /* do stuff */
  }
  # when you pass $myvar to the function, like so -
  pass( $myvar );
  # it is available inside the function as "$arg".


  # import the variable you need into the function
  function import_var(){
      global $myvar;
      # now the global $myvar is available inside the function.
      /* do stuff */
  }
  # this method is less preferable, 
  # since you cannot be sure of the current state of the global $myvar
  # (or if it even exists when the function is called)

I want two functions: 1. takes an array (just values array, no keys), cycles through them, finds their key in the $wares array, and appends it to a string. The wares are separated by a period. So you get a string like 1.4.28 that I can store in the database. 2. takes the string from the database and reverts the string back to an array.

Before going ahead with this, consider that you're defeating the purpose of using a database by encoding a bunch of data and storing it in a single field - you're effectively making it "invisible."

What if you wanted to find records of Oranges ("1")? You'd have to extract all the data, convert it back into an array, and then search for Oranges. If you have a large dataset, that's a huge waste of time. If you'd stored "Oranges" in the database directly, MySQL could've searched for you (that's its purpose in life, after all).

But anyway,

If you want to represent an array as a string (e.g., so you can store it in the DB), there's already a function to do that:

  <?php
  $array = array( 'oranges','apples','pears' );

  # convert $array into a string value
  $str = serialize( $array );

  # now you can save it to the DB, in your SESSION, whatever
  # to convert it back, use:
  $array = unserialize( $str );

  # you can also use JSON - 
  $jsonstr = json_encode( $array );

  # and convert it back into an array
  $array = json_decode( $jsonstr,true );

Okay now I've changed to serialize and unserialize. The page is "loading". It's complaining my SQL syntax isn't valid though, which I can't figure out why.

UPDATE profile SET selling=$sell, buying=$buy, motto=$motto WHERE id=1

$sell and $buy are the results of serializing the arrays, and $motto is a string.

Am I understanding correctly that $sell and $buy are the values returned by serialize()?

serialize() returns a string, which needs to be delimited by single quotes in a MySQL query. The string may also include characters (e.g., ') that need to be escaped before being used in your query.

  <?php
  $str = serialize( $array );
  # assuming $DB is an instance of mysqli
  $x_str = $DB->real_escape_string( $str );
  $query = "UPDATE `profile` SET `col`='$xstr' ...";

Honestly, though, you could be doing this in a much less complicated way.

.1. define all key=>ware pairs (including "excellent" wares):

  $wares = array(
      1 => 'iron'
     ,2 => 'oranges'
      // . . .
     ,64 => 'excellent iron'
     ,65 => 'excellent oranges'
      // . . .
  );

.2. in your form, use the keys as the values in the first place:

  <.form>
      <label>
          <input type="checkbox" name="sell[]" value="1"> Iron
      </label><br>
      <label>
          <input type="checkbox" name="sell[]" value="2"> Oranges
      </label><br>
      <!-- . . . -->
      <label>
          <input type="checkbox" name="sell[]" value="64"> Excellent Iron
      </label><br>
      <label>
          <input type="checkbox" name="sell[]" value="65"> Excellent Oranges
      </label><br>
      <!-- . . . -->
  </form>

If you're not already doing so, you can use PHP to generate this form (which would be easier, and much less error-prone, than writing it by hand):

  <?php
  # loop through $wares array and create HTML inputs
  foreach( $wares as $key => $ware ){
      $checkbox[] = '<input type="checkbox" name="sell[]" value="'. $key .'"> '. $ware;
  }

.3. now, when your user submits the form, you have a pre-made array containing the keys of the items they've checked, which you can serialize directly:

  <?php
  $sellStr = serialize( $_POST['sell'] );
  $x_sellStr = $DB->real_escape_string( $sellStr );
  $query = "UPDATE `profile` SET `selling`='$x_sellStr' . . .";

Simpler, quicker, less error-prone.

Edit

I missed @thatericsmith 's reply.

What he's describing is the same thing I was talking about in my first reply - normalization. It allows the database to "understand" the values you're storing, rather than storing a big ugly string that has to be given back to PHP before it can be searched.