How to check that vsprintf has the correct number of arguments before running

I'm trying to use vsprintf() to output a formatted string, but I need to validate that I have the correct number of arguments before running it to prevent "Too few arguments" errors.

In essence I think what I need is a regex to count the numbe开发者_Python百科r of type specifiers, but I'm pretty useless when it comes to regex and I couldn't fund it anywhere so I thought I'd give SO a go. :)

Unless you can think of a better way this method is along the lines of what I want.

function __insertVars($string, $vars = array()) {

    $regex = '';
    $total_req = count(preg_match($regex, $string));

    if($total_req === count($vars)) {
        return vsprintf($string, $vars);
    }

}

Please tell me if you can think of a simpler way.

I think your solution is the only way to more or less reliably tell how many arguments are in the string.

Here is the regular expression I came up with, use it with preg_match_all():

%[-+]?(?:[ 0]|['].)?[a]?\d*(?:[.]\d*)?[%bcdeEufFgGosxX]

Based upon sprintf() documentation. Should be compatible with PHP 4.0.6+ / 5.

EDIT - A slightly more compact version:

%[-+]?(?:[ 0]|'.)?a?\d*(?:\.\d*)?[%bcdeEufFgGosxX]

Also, take advantage of the func_get_args() and func_num_args() functions in your code.

EDIT: - Updated to support positional/swapping arguments (not tested):

function validatePrintf($format, $arguments)
{
    if (preg_match_all("~%(?:(\d+)[$])?[-+]?(?:[ 0]|['].)?(?:[-]?\d+)?(?:[.]\d+)?[%bcdeEufFgGosxX]~", $format, $expected) > 0)
    {
        $expected = intval(max($expected[1], count(array_unique($expected[1]))));

        if (count((array) $arguments) >= $expected)
        {
            return true;
        }
    }

    return false;
}

var_dump(validatePrintf('The %2$s contains %1$d monkeys', array(5, 'tree')));

I think it's very easy, because it returns FALSE value if something wrong. You can check like this:

if (vsprintf($string, $wrongArray) === false) {
    // vsprintf has wrong number of arguments
}

I used Alix Axel answer and created universal function.

We have a $countArgs (from function parameters) and $countVariables (from $format like %s).

For example:

$object->format('Hello, %s!', ['Foo']); // $countArgs = 1, $countVariables = 1;

Print: Hello, Foo!

$object->format('Hello, %s! How are you, %s?', ['Bar']); // $countArgs = 1, $countVariables = 2;

Print: Error.

Function:

public static function format($format, array $args)
{
    $pattern = "~%(?:(\d+)[$])?[-+]?(?:[ 0]|['].)?(?:[-]?\d+)?(?:[.]\d+)?[%bcdeEufFgGosxX]~";

    $countArgs = count($args);
    preg_match_all($pattern, $format, $expected);
    $countVariables = isset($expected[0]) ? count($expected[0]) : 0;

    if ($countArgs !== $countVariables) {
        throw new \Exception('The number of arguments in the string does not match the number of arguments in a template.');
    } else {
        return $countArgs > 1 ? vsprintf($format, $args) : sprintf($format, reset($args));
    }
}