PHP Conditional Operator and Self Assignment

Question

Is this sort of thing considered OK in PHP?

$foo = $_GET['foo'];
$foo = empty($foo) || !custom_is_valid($foo) ? 'default' : $foo;

Are there cleaner alternatives to this? I'm basically trying to avoid extra table look-ups.

Answer 1

Does custom_is_valid() check for an empty variable? Because being able to remove the empty() and "or not" would go a long way to improving that code.

Answer 2

With mabwi's advice you can even shorten this to:

$foo = custom_is_valid($_GET['foo']) ? $_GET['foo'] : 'default';

Answer 3

As you'll see if you turn error_reporting(E_ALL) on, that isn't really the best way to do it. PHP basically wants you to do

$foo = empty($_GET['foo']) || !custom_is_valid($_GET['foo']) ? 'default' : $_GET['foo'];

Answer 4

By default, if you assign $foo the value in $_GET['foo'], $foo is just a reference to the $_GET array index... PHP makes reference copies of variables by default to optimize code.

The best way would to write something like this:

$foo = (isset($_GET['foo']) && custom_is_valid($_GET['foo'])) ? ($_GET['foo']) : ('default');

function custom_is_valid($toCheck)
{
    if ($toCheck != '')
    {
        //Do some checking
        return true;
    }
    else
        return false;
}

Answer 5

How about:

$foo = 'default';
if (array_key_exists('foo', $_GET) and custom_is_valid($_GET['foo'])) {
    $foo = $_GET['foo'];
}

And don't be afraid of the array lookups, they are not that slow :)

Answer 6

Perhaps instead of just checking if it is valid, run it though a cleaning function that takes a default.

Also, I like to use the following function so I don't get warnings on accessing non-existant array keys when running E_STRICT:

function GetVar($var, $default = '') {
  $value = $default;
  if(isset($_GET[$var])) {
    $value = $_GET[$var];
  }
  return $value;
}

function custom_clean($value, $default = '') {
  ... validation logic or return $default ...
}

$foo = custom_clean(GetVar('foo'), 'default');

Answer 7

A class here would make your life a lot easier.

<?php

class ParamHelper
{
  protected $source;

  public function __construct( array $source )
  {
    $this->source = $source;
  }

  public function get( $key, $default=null, $validationCallback=null )
  {
    if ( isset( $this->source[$key] ) && !empty( $this->source[$key] ) )
    {
      if ( is_null( $validationCallback ) || ( !is_null( $validationCallback ) && call_user_func( $validationCallback, $this->source[$key] ) ) )
      {
        return $this->source[$key];
      }
    }
    return $default;
  }
}

// Just for the demo
function validateUpper( $value )
{
  return ( $value == strtoupper( $value ) );
}

// Mimic some query-string values
$_GET['foo'] = 'bar';
$_GET['bar'] = 'BAZ';
$_GET['lol'] = 'el oh el';

$getHelper = new ParamHelper( $_GET );

echo $getHelper->get( 'foo', 'foo default', 'validateUpper' ), '<br>';
echo $getHelper->get( 'bar', 'bar default', 'validateUpper' ), '<br>';
echo $getHelper->get( 'baz', 'baz default' ), '<br>';
echo $getHelper->get( 'lol' ), '<br>';
echo $getHelper->get( 'rofl' ), '<br>';