assert
(PHP 4, PHP 5, PHP 7)
assert — 检查一个断言是否为 FALSE
说明
PHP 5
PHP 7
assert() 会检查指定的
assertion 并在结果为 FALSE 时采取适当的行动。
Traditional assertions (PHP 5 and 7)
如果 assertion 是字符串，它将会被 assert() 当做 PHP 代码来执行。
assertion 是字符串的优势是当禁用断言时它的开销会更小，并且在断言失败时消息会包含 assertion 表达式。
这意味着如果你传入了 boolean 的条件作为 assertion，这个条件将不会显示为断言函数的参数；在调用你定义的 assert_options() 处理函数时，条件会转换为字符串，而布尔值 FALSE 会被转换成空字符串。
断言这个功能应该只被用来调试。
你应该用于完整性检查时测试条件是否始终应该为 TRUE，来指示某些程序错误，或者检查具体功能的存在（类似扩展函数或特定的系统限制和功能）。
断言不应该用于普通运行时操作，类似输入参数的检查。 作为一个经验法则，在断言禁用时你的代码也应该能够正确地运行。
assert() 的行为可以通过 assert_options() 来配置，或者手册页面上描述的 .ini 设置。
assert_options() ASSERT_CALLBACK 配置指令允许设置回调函数来处理失败的断言。
assert() 回调函数在构建自动测试套件的时候尤其有用，因为它们允许你简易地捕获传入断言的代码，并包含断言的位置信息。 当信息能够被其他方法捕获，使用断言可以让它更快更方便！
回调函数应该接受三个参数。
第一个参数包括了断言失败所在的文件。
第二个参数包含了断言失败所在的行号，第三个参数包含了失败的表达式（如有任意 — 字面值例如 1 或者 "two" 将不会传递到这个参数）。
PHP 5.4.8 及更高版本的用户也可以提供第四个可选参数，如果设置了，用于将 description 指定到 assert()。
Expectations (PHP 7 only)
assert() is a language construct in PHP 7, allowing for the definition of expectations: assertions that take effect in development and testing environments, but are optimised away to have zero cost in production.
While assert_options() can still be used to control behaviour as described above for backward compatibility reasons, PHP 7 only code should use the two new configuration directives to control the behaviour of assert() and not call assert_options().
| Directive | Default value | Possible values |
|---|---|---|
| zend.assertions | 1 |
|
| assert.exception | 0 |
|
参数
-
assertion -
断言。In PHP 5, this must be either a string to be evaluated or a boolean to be tested. In PHP 7, this may also be any expression that returns a value, which will be executed and the result used to indicate whether the assertion succeeded or failed.
-
description -
如果
assertion失败了，选项 description 将会包括在失败信息里。 -
exception -
In PHP 7, the second parameter can be a Throwable object instead of a descriptive string, in which case this is the object that will be thrown if the assertion fails and the assert.exception configuration directive is enabled.
返回值
assertion 是 false 则返回 FALSE，否则是 TRUE。
更新日志
| 版本 | 说明 |
|---|---|
| 7.0.0 |
assert() is now a language construct and not a
function. assertion() can now be an expression.
The second parameter is now interpreted either as an
exception (if a
Throwable object is given), or as the
description supported from PHP 5.4.8 onwards.
|
| 5.4.8 |
增加了参数 description。
description 现在也作为第四个参数提供给 ASSERT_CALLBACK 模式里的回调函数。
|
范例
Traditional assertions (PHP 5 and 7)
Example #1 使用自定义处理程序处理失败的断言
<?php
// 激活断言，并设置它为 quiet
assert_options(ASSERT_ACTIVE, 1);
assert_options(ASSERT_WARNING, 0);
assert_options(ASSERT_QUIET_EVAL, 1);
//创建处理函数
function my_assert_handler($file, $line, $code)
{
echo "<hr>Assertion Failed:
File '$file'<br />
Line '$line'<br />
Code '$code'<br /><hr />";
}
// 设置回调函数
assert_options(ASSERT_CALLBACK, 'my_assert_handler');
// 让一则断言失败
assert('mysql_query("")');
?>
Example #2 使用自定义处理器打印描述信息
<?php
// 激活断言，并设置它为 quiet
assert_options(ASSERT_ACTIVE, 1);
assert_options(ASSERT_WARNING, 0);
assert_options(ASSERT_QUIET_EVAL, 1);
//创建处理函数
function my_assert_handler($file, $line, $code, $desc = null)
{
echo "Assertion failed at $file:$line: $code";
if ($desc) {
echo ": $desc";
}
echo "\n";
}
// 设置回调函数
assert_options(ASSERT_CALLBACK, 'my_assert_handler');
// Make an assertion that should fail
assert('2 < 1');
assert('2 < 1', 'Two is less than one');
?>
以上例程会输出：
Assertion failed at test.php:21: 2 < 1 Assertion failed at test.php:22: 2 < 1: Two is less than one
Expectations (PHP 7 only)
Example #3 Expectations without a custom exception
<?php
assert(true == false);
echo 'Hi!';
?>
With zend.assertions set to 0, the above example will output:
Hi!
With zend.assertions set to 1 and assert.exception set to 0, the above example will output:
Warning: assert(): assert(true == false) failed in - on line 2 Hi!
With zend.assertions set to 1 and assert.exception set to 1, the above example will output:
Fatal error: Uncaught AssertionError: assert(true == false) in -:2
Stack trace:
#0 -(2): assert(false, 'assert(true == ...')
#1 {main}
thrown in - on line 2
Example #4 Expectations with a custom exception
<?php
class CustomError extends AssertionError {}
assert(true == false, new CustomError('True is not false!'));
echo 'Hi!';
?>
With zend.assertions set to 0, the above example will output:
Hi!
With zend.assertions set to 1 and assert.exception set to 0, the above example will output:
Warning: assert(): CustomError: True is not false! in -:4
Stack trace:
#0 {main} failed in - on line 4
Hi!
With zend.assertions set to 1 and assert.exception set to 1, the above example will output:
Fatal error: Uncaught CustomError: True is not false! in -:4
Stack trace:
#0 {main}
thrown in - on line 4