is_bool()

(PHP 4, PHP 5, PHP 7)

检测变量是否是布尔型

描述

is_bool(mixed $var): bool

如果$var是boolean则返回TRUE。

Example #1is_bool()示例

<?php
$a = false;
$b = 0;
// 因为 $a 是布尔型，所以结果为真
if (is_bool($a)) {
    print "Yes, this is a boolean";
}
// 因为 $b 不是布尔型，所以结果为非真
if (is_bool($b)) {
    print "Yes, this is a boolean";
}
?>

参见is_array()、is_float()、is_int()、is_integer()、is_string()和is_object()。

It should be stated that this function returns true if the _type_ of it's argument is boolean. It does not convert or coerce the value to a boolean type, not sure why so many comments focus on how to do this.
However, if you arrived here looking for a solution to convert a value to a boolean type, use this:
to_bool($x) { return (bool)$x; }

The function Michael Smith published doesn't do the work as it should.
To check if a variable is boolean is one thing, to evaluate if the value of a variable represents a boolean condition (true or false) is another.
Here a simple function that checks the status of the received variable in regards to boolean equivalencies (case insensitive).
<?php
/** 
 * Check "Booleanic" Conditions :)
 *
 * @param [mixed] $variable Can be anything (string, bol, integer, etc.)
 * @return [boolean]      Returns TRUE for "1", "true", "on" and "yes"
 *               Returns FALSE for "0", "false", "off" and "no"
 *               Returns NULL otherwise.
 */
function is_enabled($variable)
{
  if (!isset($variable)) return null;
  return filter_var($variable, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE);
}
?>
Of course, it is a simplistic approach, but for the majority of cases it will do the job right.
And, just to put thing in the right perspective, here's a real function that does what Phill disclosed:
<?php
/** 
 * Convert $variable to boolean (adapted from Phill answer)
 *
 * @param [mixed] $variable Can be anything
 * @return [boolean]      Returns the booelan equivalent to $variable based on Zend Enegine interpretation
 */
function to_bool($variable) 
{ 
  return (bool)$variable;
}
?>
I hope it helps someone. Happy coding.

The function in the last comment also converts the string 'false' to a true boolean. Here's a function that does what I think was intended:
<?php
function toBool($var) {
 if (!is_string($var)) return (bool) $var;
 switch (strtolower($var)) {
  case '1':
  case 'true':
  case 'on':
  case 'yes':
  case 'y':
   return true;
  default:
   return false;
 }
}