(PHP 4, PHP 5, PHP 7, PHP 8)
assert — 檢查一個(gè)斷言是否為 false
PHP 5
PHP 7
assert() 會(huì)檢查指定的
assertion 并在結(jié)果為 false 時(shí)采取適當(dāng)?shù)男袆?dòng)。
如果 assertion 是字符串，它將會(huì)被 assert() 當(dāng)做 PHP 代碼來執(zhí)行。
assertion 是字符串的優(yōu)勢(shì)是當(dāng)禁用斷言時(shí)它的開銷會(huì)更小，并且在斷言失敗時(shí)消息會(huì)包含 assertion 表達(dá)式。
這意味著如果你傳入了 boolean 的條件作為 assertion，這個(gè)條件將不會(huì)顯示為斷言函數(shù)的參數(shù)；在調(diào)用你定義的 assert_options() 處理函數(shù)時(shí)，條件會(huì)轉(zhuǎn)換為字符串，而布爾值 false 會(huì)被轉(zhuǎn)換成空字符串。
斷言這個(gè)功能應(yīng)該只被用來調(diào)試。
你應(yīng)該用于完整性檢查時(shí)測(cè)試條件是否始終應(yīng)該為 true，來指示某些程序錯(cuò)誤，或者檢查具體功能的存在（類似擴(kuò)展函數(shù)或特定的系統(tǒng)限制和功能）。
斷言不應(yīng)該用于普通運(yùn)行時(shí)操作，類似輸入?yún)?shù)的檢查。 作為一個(gè)經(jīng)驗(yàn)法則，在斷言禁用時(shí)你的代碼也應(yīng)該能夠正確地運(yùn)行。
assert() 的行為可以通過 assert_options() 來配置，或者手冊(cè)頁面上描述的 .ini 設(shè)置。
assert_options() ASSERT_CALLBACK 配置指令允許設(shè)置回調(diào)函數(shù)來處理失敗的斷言。
assert() 回調(diào)函數(shù)在構(gòu)建自動(dòng)測(cè)試套件的時(shí)候尤其有用，因?yàn)樗鼈冊(cè)试S你簡(jiǎn)易地捕獲傳入斷言的代碼，并包含斷言的位置信息。 當(dāng)信息能夠被其他方法捕獲，使用斷言可以讓它更快更方便！
回調(diào)函數(shù)應(yīng)該接受三個(gè)參數(shù)。
第一個(gè)參數(shù)包括了斷言失敗所在的文件。
第二個(gè)參數(shù)包含了斷言失敗所在的行號(hào)，第三個(gè)參數(shù)包含了失敗的表達(dá)式（如有任意 — 字面值例如 1 或者 "two" 將不會(huì)傳遞到這個(gè)參數(shù)）。
PHP 5.4.8 及更高版本的用戶也可以提供第四個(gè)可選參數(shù)，如果設(shè)置了，用于將 description 指定到 assert()。
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 |
|
assertion斷言。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 失敗了，選項(xiàng) description 將會(huì)包括在失敗信息里。
exceptionIn 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.
assertion 是 false 則返回 false，否則是 true。
| 版本 | 說明 |
|---|---|
| 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 |
增加了參數(shù) description。
description 現(xiàn)在也作為第四個(gè)參數(shù)提供給 ASSERT_CALLBACK 模式里的回調(diào)函數(shù)。
|
示例 #1 使用自定義處理程序處理失敗的斷言
<?php
// 激活斷言，并設(shè)置它為 quiet
assert_options(ASSERT_ACTIVE, 1);
assert_options(ASSERT_WARNING, 0);
assert_options(ASSERT_QUIET_EVAL, 1);
//創(chuàng)建處理函數(shù)
function my_assert_handler($file, $line, $code)
{
echo "<hr>Assertion Failed:
File '$file'<br />
Line '$line'<br />
Code '$code'<br /><hr />";
}
// 設(shè)置回調(diào)函數(shù)
assert_options(ASSERT_CALLBACK, 'my_assert_handler');
// 讓一則斷言失敗
assert('mysql_query("")');
?>
示例 #2 使用自定義處理器打印描述信息
<?php
// 激活斷言，并設(shè)置它為 quiet
assert_options(ASSERT_ACTIVE, 1);
assert_options(ASSERT_WARNING, 0);
assert_options(ASSERT_QUIET_EVAL, 1);
//創(chuàng)建處理函數(shù)
function my_assert_handler($file, $line, $code, $desc = null)
{
echo "Assertion failed at $file:$line: $code";
if ($desc) {
echo ": $desc";
}
echo "\n";
}
// 設(shè)置回調(diào)函數(shù)
assert_options(ASSERT_CALLBACK, 'my_assert_handler');
// Make an assertion that should fail
assert('2 < 1');
assert('2 < 1', 'Two is less than one');
?>
以上例程會(huì)輸出：
Assertion failed at test.php:21: 2 < 1 Assertion failed at test.php:22: 2 < 1: Two is less than one
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