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functions, classes, and objects -- oh my!

by: misterhaan

Page: 5 of 5
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terms and comparisons

we'll start out with a review of the terms that came up: class - a collection of variables and / or functions constructor - the special function that a class may have, which is executed when an object is created from that class; the constructor must have the same name as the class member - member variables and member functions are variables and functions that are defined inside of a class object - an instance of a class; a variable created from a class that then gains the properties defined in the class; an object reference uses -> oop - object-oriented programming; programming based on objects static - static references use the name of the class and do not require an object to be created; a static reference uses ::

php uses the same syntax for classes and objects as c++ does, in that static functions are accessed by classname::functionname and object functions are accessed by objectname->functionname. some other languages (java for example) use classname.functionname and objectname.functionname instead. both c++ and java allow for parts of the class to be defined as private, which means that you absolutely cannot access those parts of the class from outside the class -- php does not currently support this. java also requires that static functions be specifically defined as static (c++ may support this as well) -- php will let you call any function statically or from an object (though it may not work!). very generally, php supports the use of objects and classes, but it is not at all strict in its implementation.

to wrap things up, I'll show you a more complete example, which is my (somewhat) current FORM class:

<?
  class FORM {
    var $indent;

function FORM($action = null, $method = 'post', $indent = '      ', $id = '') {
      if($action === null)
        $action = $_SERVER['PHP_SELF'];
      echo $indent . '<form action="' . $action . '" method="' . $method . (strlen($id) ? '" id="' . $id : '') . '"><div>' . "n";
      $this->indent = $indent;
    }

function end($buttontext = '') {
      if(is_array($buttontext)) {
        echo $this->indent . '  <div class="buttons">' . "n";
        foreach($buttontext as $text)
          echo $this->indent . '    <input type="submit" name="submit" value="' . $text . '" />' . "n";

echo $this->indent . '  </div>' . "n";
      } elseif(strlen($buttontext) > 0)
        echo $this->indent . '  <div class="buttons"><input type="submit" name="submit" value="' . $buttontext . '" /></div>' . "n";
      echo $this->indent . '</div></form>' . "nn";
    }

function startset($title = '', $class = '', $id = '') {
      if(strlen($class) > 0)
        $class = ' class="' . $class . '"';
      if(strlen($id) > 0)
        $id = ' id="' . $id . '"';
      $this->indent .= '  ';
      echo $this->indent . '<fieldset' . $class . $id . '>' . "n";
      if(strlen($title) > 0)
        echo $this->indent . '  <legend>' . $title . '</legend>' . "n";
    }

function endset($buttontext = '') {
      if(strlen($buttontext) > 0)
        echo $this->indent . '  <div class="buttons"><input type="submit" name="submit" value="' . $buttontext . '" /></div>' . "n";
      echo $this->indent . '</fieldset>' . "n";
      $this->indent = substr($this->indent, 2);
    }

function label($text, $for = '') {
      echo $this->indent . '  <label' . (strlen($for) > 0 ? ' for="fld' . $for . '"' : '') . '>' . $text . '</label>' . "n";
    }

function input($name, $value = null, $maxlength = null) {
      echo $this->indent . '  <input id="fld' . $name . '" name="' . $name . '" class="field"' . ($maxlength === null ? '' : ' maxlength="' . $maxlength . '"') . ($value === null ? '' : ' value="' . $value . '"') . ' />' . "n";
    }

function password($name, $maxlength = null) {
      echo $this->indent . '  <input id="fld' . $name . '" name="' . $name . '" class="field" type="password"' . ($maxlength === null ? '' : ' maxlength="' . $maxlength . '"') . ' />' . "n";
    }

function hidden($name, $value) {
      echo $this->indent . '  <input type="hidden" name="' . $name . '" value="' . $value . '" />' . "n";
    }

function textarea($name, $value = '', $maxlength = null) {
      echo $this->indent . '  <textarea name="' . $name . '" id="fld' . $name . '"' . ($maxlength !== null ? ' maxlength="' . $maxlength . '"' : '') . '>' . $value . '</textarea>' . "n";
    }

function select($name, $values, $text, $default = null) {
      echo $this->indent . '  <select id="fld' . $name . '" name="' . $name . '" class="field">' . "n";
      for($i = 0; $i < count($values); $i++)
        echo $this->indent . '    <option' . ($values[$i] === $default ? ' selected="selected"' : '') . ($text[$i] === null ? '>' . $values[$i] : ' value="' . $values[$i] . '">' . $text[$i]) . '</option>' . "n";
      echo $this->indent . '  </select>' . "n";
    }

function checkbox($name, $checked = false) {
      echo $this->indent . '  <input type="checkbox" id="fld' . $name . '" name="' . $name . '" class="checkbox"' . ($checked ? ' checked="checked"' : '') . ' />' . "n";
    }
  }
?>

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