Test if string could be boolean PHP

If you use the flag FILTER_NULL_ON_FAILURE, filter_var() will work nicely:

function CheckBool($Value) {
  return null !== filter_var($Value, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE);
}

There's, by the way, a cleaner way of writing it:

function checkBool($string){
    $string = strtolower($string);
    return (in_array($string, array("true", "false", "1", "0", "yes", "no"), true));
}

But yes. The one you wrote down is the only way.

You can either use is_bool() or as suggested on php.net:

<?php
$myString = "On";
$b = filter_var($myString, FILTER_VALIDATE_BOOLEAN);
?>

http://php.net/manual/en/function.is-bool.php

The latter one will accept strings like "on" and "yes" as true as well.