Member and Function Inheritance in PHP

Question

I'm still new to PHP and I am having a lot of trouble. I'm used to languages like C,C++, and Java, and this one is kinda confusing me. Basically my problem is that I have the following code:

class File_Reader 
{

    protected $text;

    public function Scan_File (){}

    public function Skip_Whitespace(&$current_pos)
    {
        //skip past whitespace at the start
        while (($current_pos < strlen($text) && ($text[$current_pos] == ' ')))
            $current_pos++;
    }

    public function __construct(&$file_text)
    {
        $text = $file_text;
    }
}

class Times_File_Reader extends File_Reader
 {
     Public Function Scan_File()
     {
         $errors = array();
         $times = array();
         $current_time;
         $cursor = 0;
         $line = 0;
         while ($cursor < strlen($text))
         {

             Skip_Whitespace($cursor);
             //....lots more code here...
             return $times;
         }
     }
 }

but when I try to run it, it tells me that $time and Skip_Whitespace are both undefined. I don't understand, they should have been inherited. I tried putting an echo command in the File_Reader constructor and it does enter the constructor when I create my Times_File_Reader.

Oh, and for completeness, here is where I declare my Times_File_Reader:

   include 'File_Readers.php';

  $text = file_get_contents("01_CT.txt");
  $reader = new Times_File_Reader($text);
  $array = $reader->Scan_File();

I've been searching for an answer for hours to no avail, and deadline is approaching quickly. Any help would be appreciated. Thank you!

Paul Hulett · Accepted Answer · 2013-04-11 23:32:51Z

2

I believe that you need to note that you are using the class function by using

$this->Skip_Whitespace($cursor);

answered Apr 11, 2013 at 23:32

Paul Hulett

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2 Comments

Phill Sparks Over a year ago

It goes deeper than just $this->Skip_Whitespace($cursor); you also need to use $this->text as the next answer suggests.

Paul Hulett Over a year ago

@PhillSparks you are correct. I was confused by his reference to $time, when I think he meant $text.

calumbrodie · Accepted Answer · 2013-04-11 23:37:42Z

1

You need to set the property that you are passing into your constructor as a property of the class (the variables within methods are scoped in the same way as Java).

You do this using $this->property

// File_Reader
public function __construct(&$file_text)
{
    $this->text = $file_text;
}

// Times_File_Reader
public function Scan_File()
{
    $errors = array();
    $times = array();
    $current_time;
    $cursor = 0;
    $line = 0;
    while ($cursor < strlen($this->text))
    {
        $this->Skip_Whitespace($cursor);
        //....lots more code here...
        return $times;
    }
}

Edit - as an aside you seem to be using some wacky underscorecase/Titlecase hybrid. Best practice in PHP is to use lowerCamelCase for methods and CamelCase for class names.

class FileReader
class TimesFileReader
public function scanFile()

Also - you are passing your variables by reference (&$var) - you probably don't have to do this (the only valid use case I can think of for this is in certain situations using closures/anonymous functions). I'll admit the docs on this are not very clear. http://schlueters.de/blog/archives/125-Do-not-use-PHP-references.html

public function __construct($file_text)
{
    $this->text = $file_text;
}

edited Apr 11, 2013 at 23:37

answered Apr 11, 2013 at 23:32

calumbrodie

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3 Comments

James - not really a pirate Over a year ago

Ok, this is helping. Thank you! However, I still cannot use Skip_Whitespace($cursor); The error it gives me is: Fatal error: Call to undefined function Skip_Whitespace() in C:\xampp\htdocs\Software-Engineering\File_Readers.php on line 58 Any clue why that part is not working?

calumbrodie Over a year ago

Again - you need to use $this->method(). Updated the code accordingly.

James - not really a pirate Over a year ago

Ok. Thank you. Also, as far as the "wacky underscorecase/Titlecase hybrid" goes, that was not my choice. Team captain does not like camel case for some reason and refused to let it be part of our coding standards. :\

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