is_bool

(PHP 4, PHP 5, PHP 7, PHP 8)

is_bool — 检测变量是否是布尔值

说明

is_bool ( mixed $value ) : bool

检查变量是否为布尔值。

参数

value

要检查的变量。

返回值

如果 value 是布尔值则返回 true，否则返回 false。

范例

Example #1 is_bool() 示例

<?php
$a = false;
$b = 0;

// 因为 $a 是布尔值，所以结果为 true
if (is_bool($a) === true) {
    echo "Yes, this is a boolean";
}

// 因为 $b 不是布尔值，所以结果为 false
if (is_bool($b) === false) {
    echo "No, this is not a boolean";
}
?>

参见

User Contributed Notes

Julio Marchi 08-Sep-2019 12:32
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.
phil 10-Jan-2019 06:21
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; }
Michael Smith 17-Nov-2013 01:17
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;
  }
}