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說明

PHP 5

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

PHP 7

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

assert() 會檢查指定的 assertion 并在結(jié)果為 false 時采取適當(dāng)?shù)男袆印?

Traditional assertions (PHP 5 and 7)

如果 assertion 是字符串，它將會被 assert() 當(dāng)做 PHP 代碼來執(zhí)行。 assertion 是字符串的優(yōu)勢是當(dāng)禁用斷言時它的開銷會更小，并且在斷言失敗時消息會包含 assertion 表達式。這意味著如果你傳入了 boolean 的條件作為 assertion，這個條件將不會顯示為斷言函數(shù)的參數(shù)；在調(diào)用你定義的 assert_options() 處理函數(shù)時，條件會轉(zhuǎn)換為字符串，而布爾值 false 會被轉(zhuǎn)換成空字符串。

斷言這個功能應(yīng)該只被用來調(diào)試。你應(yīng)該用于完整性檢查時測試條件是否始終應(yīng)該為 true，來指示某些程序錯誤，或者檢查具體功能的存在（類似擴展函數(shù)或特定的系統(tǒng)限制和功能）。

斷言不應(yīng)該用于普通運行時操作，類似輸入?yún)?shù)的檢查。作為一個經(jīng)驗法則，在斷言禁用時你的代碼也應(yīng)該能夠正確地運行。

assert() 的行為可以通過 assert_options() 來配置，或者手冊頁面上描述的 .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)建自動測試套件的時候尤其有用，因為它們允許你簡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)該接受三個參數(shù)。第一個參數(shù)包括了斷言失敗所在的文件。第二個參數(shù)包含了斷言失敗所在的行號，第三個參數(shù)包含了失敗的表達式（如有任意 — 字面值例如 1 或者 "two" 將不會傳遞到這個參數(shù)）。 PHP 5.4.8 及更高版本的用戶也可以提供第四個可選參數(shù)，如果設(shè)置了，用于將 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().

PHP 7 configuration directives for **assert()**
Directive	Default value	Possible values
zend.assertions	`1`	`1`: generate and execute code (development mode) `0`: generate code but jump around it at runtime `-1`: do not generate code (production mode)
assert.exception	`0`	`1`: throw when the assertion fails, either by throwing the object provided as the `exception` or by throwing a new AssertionError object if `exception` wasn't provided `0`: use or generate a Throwable as described above, but only generate a warning based on that object rather than throwing it (compatible with PHP 5 behaviour)

參數(shù)

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 description 將會包括在失敗信息里。
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 則返回 false，否則是 true。

更新日志

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)在也作為第四個參數(shù)提供給 `ASSERT_CALLBACK` 模式里的回調(diào)函數(shù)。

范例

Traditional assertions (PHP 5 and 7)

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');
?>

以上例程會輸出：

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

參見

assert_options() - 設(shè)置/獲取斷言的各種標志