PHP: Type Hinting – Manual

Found this little Gem today by  Daniel dot L dot Wood at Gmail dot Com;

People often ask about scalar/basic typehints.  Here is a drop in class that I use in my MVC framework that will enable typehints through the use of a custom error handler.

Note: You should include this code above all other code in your include headers and if you are the using set_error_handler() function you should be aware that this uses it as well.  You may need to chain your set_error_handlers()

Why?
1) Because people are sick of using the is_* functions to validate parameters.
2) Reduction of redundant coding for defensive coders.
3) Functions/Methods are self defining/documenting as to required input.

Also..
Follow the discussion for typehints in PHP 6.0 on the PHP Internals boards.

[cc lang=”php”]
< ?php define('TYPEHINT_PCRE' ,'/^Argument (\d)+ passed to (?:(\w+)::)?(\w+)\(\) must be an instance of (\w+), (\w+) given/'); class Typehint { private static $Typehints = array( 'boolean' => ‘is_bool’,
‘integer’ => ‘is_int’,
‘float’ => ‘is_float’,
‘string’ => ‘is_string’,
‘resrouce’ => ‘is_resource’
);

private function __Constrct() {}

public static function initializeHandler()
{

set_error_handler(‘Typehint::handleTypehint’);

return TRUE;
}

private static function getTypehintedArgument($ThBackTrace, $ThFunction, $ThArgIndex, &$ThArgValue)
{

foreach ($ThBackTrace as $ThTrace)
{

// Match the function; Note we could do more defensive error checking.
if (isset($ThTrace[‘function’]) && $ThTrace[‘function’] == $ThFunction)
{

$ThArgValue = $ThTrace[‘args’][$ThArgIndex – 1];

return TRUE;
}
}

return FALSE;
}

public static function handleTypehint($ErrLevel, $ErrMessage)
{

if ($ErrLevel == E_RECOVERABLE_ERROR)
{

if (preg_match(TYPEHINT_PCRE, $ErrMessage, $ErrMatches))
{

list($ErrMatch, $ThArgIndex, $ThClass, $ThFunction, $ThHint, $ThType) = $ErrMatches;

if (isset(self::$Typehints[$ThHint]))
{

$ThBacktrace = debug_backtrace();
$ThArgValue = NULL;

if (self::getTypehintedArgument($ThBacktrace, $ThFunction, $ThArgIndex, $ThArgValue))
{

if (call_user_func(self::$Typehints[$ThHint], $ThArgValue))
{

return TRUE;
}
}
}
}
}

return FALSE;
}
}
Typehint::initializeHandler();
?>
[/cc]
An are some examples of the class in use:
[cc lang=”php”]
< ?php function teststring(string $string) { echo $string; } function testinteger(integer $integer) { echo $integer; } function testfloat(float $float) { echo $float; } // This will work for class methods as well. ?>
[/cc]

You get the picture..
via PHP: Type Hinting – Manual.

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