Deciphering a function

A short time ago, this function was posted in an answer to a question. As a learner, I am interested in understanding the function. However, I can't get it to work as is. The poster did not say that he had tested the function, so it could have been a "conceptual" post, meant to show direction. OTOH, I may not be invoking it correctly. Please help as I have spent some time trying to understand it.

(The $data array is one that I just put in to run the function.)

<?php

    $data = array("a" => "January", "b" => "February", "c" => "March" );

    rend开发者_如何转开发er_table ( $data ) ;
    echo $html ;

    //===========================================

    function render_table($data) {
      $html = '<table>';
      $tr = array();
      foreach (array_keys($data[0]) as $key) {
        $tr[] = '<th>' . htmlspecialchars($key) . '</th>';
      }
      $html .= "\n" . '<thead>' . "\n" . '<tr>' . "\n" . implode("\n", $tr) . '</tr>' . '</thead>';
      $tbody = array();
      foreach ($data as $row) {
        $tr = array();
        foreach ($row as $value) {
          $tr[] = '<td>' . htmlspecialchars($value) . '</td>';
        }
        $tbody[] = '<tr>' . "\n" . implode("\n", $tr) . '</tr>';
      }
      $html .= "\n" . '<tbody>' . "\n" . implode("\n", $tbody) . '</tbody>';
      $html .= '</table>';
      return $html;
    }

    ?>

First off, your data is wrong. The function takes an array of arrays as an argument.

Note the line

  foreach (array_keys($data[0]) as $key) {

...this function call is wrong as well; it should NOT be taking the first element, it should be taking the entire array, since it is using the keys from the array.

Try this: first, change the call to array_keys to use the entire array, i.e.

foreach(array_keys($data AS $key)

then change your input, and the function call:

$data= array(
  'data1' => array('one','two','three'),
  'data2' => array('four','five','six'),
  'data3' => array('seven','eight','nine')  
);
echo render_table($data);

Try this way:

<?php

$data = array("a" => "January", "b" => "February", "c" => "March" );

$html = render_table ( $data ) ;
echo $html ;

//===========================================

function render_table($data) {
  $html = '<table>';
  $tr = array();
  foreach (array_keys($data[0]) as $key) {
    $tr[] = '<th>' . htmlspecialchars($key) . '</th>';
  }
  $html .= "\n" . '<thead>' . "\n" . '<tr>' . "\n" . implode("\n", $tr) . '</tr>' . '</thead>';
  $tbody = array();
  foreach ($data as $row) {
    $tr = array();
    foreach ($row as $value) {
      $tr[] = '<td>' . htmlspecialchars($value) . '</td>';
    }
    $tbody[] = '<tr>' . "\n" . implode("\n", $tr) . '</tr>';
  }
  $html .= "\n" . '<tbody>' . "\n" . implode("\n", $tbody) . '</tbody>';
  $html .= '</table>';
  return $html;
}

?>

It basically creates a table view of the $data.

The function creates a table to view the data that is passed to it. In your code, you have

...
render_table ( $data ) ;
echo $html ;

However, $html in this case is empty. The variable created in the render_table function isn't passed outside the function unless you assign the return value of the function to a variable, like this:

...
$html = render_table ( $data ) ;
echo $html ;

Then it echoes the table HTML.