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assert

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

assert检查断言是否为 false

说明

PHP 5 和 7

assert(mixed $assertion, string $description = ?): bool

PHP 7

assert(mixed $assertion, Throwable $exception = ?): bool

assert() 会检查指定的 assertion 并在结果为 false 时采取适当的行动。

传统断言(PHP 5 和 7)

如果 assertion 是字符串,它将会被 assert() 当做 PHP 代码来执行。如果传入了 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。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() 和/或 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() 是 PHP 7 中的语言结构,允许定义 expectation:断言在开发和测试环境中生效,经过优化,在生产环境中零成本。

出于向后兼容的原因,assert_options() 仍然可以控制如上所述的行为。但仅限 PHP 7 的代码应使用两个新的配置指令来控制 assert() 的行为,而不是调用 assert_options()

用于 assert() 的 PHP 7 控制指令
指令 默认值 可能值
zend.assertions 1
  • 1:生成并执行代码(开发模式)
  • 0:生成代码但在运行时跳转
  • -1:生成代码但在运行时跳转(生产模式)
assert.exception 0
  • 1:断言失败时抛出,抛出提供给 exception 的对象,或未提供 exception 时抛出新的 AssertionError 对象
  • 0:如上所述使用/生成 Throwable,但仅仅是基于该对象生成警告而不是抛出(与 PHP 5 行为兼容)

参数

assertion

断言。In PHP 5, this must be either a string to be evaluated or a bool 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.

警告

自 PHP 7.2.0 起弃用 string 作为 assertion,自 PHP 8.0.0 起删除。

description

如果 assertion 失败了,选项 description 将会包括在失败信息里。 From PHP 7, if no description is provided, a default description equal to the source code for the invocation of assert() is provided.

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
8.0.0 assert() will no longer evaluate string arguments, instead they will be treated like any other argument. assert($a == $b) should be used instead of assert('$a == $b'). The assert.quiet_eval php.ini directive and the ASSERT_QUIET_EVAL constant have also been removed, as they would no longer have any effect.
8.0.0 Declaring a function called assert() inside a namespace is no longer allowed, and issues E_COMPILE_ERROR.
7.3.0 Declaring a function called assert() inside a namespace became deprecated. Such declaration now emits an E_DEPRECATED.
7.2.0 Usage of a string as the assertion became deprecated. It now emits an E_DEPRECATED notice when both assert.active and zend.assertions are set to 1.
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.

范例

传统断言(PHP 5 和 7)

示例 #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_ACTIVE1);
assert_options(ASSERT_WARNING0);
assert_options(ASSERT_QUIET_EVAL1);

//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("")');
?>

示例 #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_ACTIVE1);
assert_options(ASSERT_WARNING0);
assert_options(ASSERT_QUIET_EVAL1);

// 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
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)

示例 #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

示例 #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

参见

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