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assert (PHP 4, PHP 5) assert -- Checks if assertion is FALSEDescriptionbool assert ( mixed assertion )
assert() will check the given
assertion and take appropriate action if
its result is FALSE.
If the assertion is given as a string it
will be evaluated as PHP code by assert().
The advantages of a string assertion are
less overhead when assertion checking is off and messages
containing the assertion expression when
an assertion fails. This means that if you pass a boolean condition
as assertion this condition will not show up as
parameter to the assertion function which you may have defined with the
assert_options() function, the condition is converted
to a string before calling that handler function, and the boolean FALSE
is converted as the empty string.
Assertions should be used as a debugging feature only. You may
use them for sanity-checks that test for conditions that should
always be TRUE and that indicate some programming errors if not
or to check for the presence of certain features like extension
functions or certain system limits and features.
Assertions should not be used for normal runtime operations like
input parameter checks. As a rule of thumb your code should
always be able to work correctly if assertion checking is not
activated.
The behavior of assert() may be configured by
assert_options() or by .ini-settings described
in that functions manual page.
The assert_options() function and/or
ASSERT_CALLBACK configuration directive allow a callback function
to be set to handle failed assertions.
assert() callbacks are particularly useful for
building automated test suites because they allow you to easily
capture the code passed to the assertion, along with information
on where the assertion was made. While this information can be
captured via other methods, using assertions makes it much faster
and easier!
The callback function should accept three arguments. The first
argument will contain the file the assertion failed in. The
second argument will contain the line the assertion failed on and
the third argument will contain the expression that failed (if
any - literal values such as 1 or "two" will not be passed via
this argument)
Пример 1. Handle a failed assertion with a custom handler |
<?php
assert_options(ASSERT_ACTIVE, 1);
assert_options(ASSERT_WARNING, 0);
assert_options(ASSERT_QUIET_EVAL, 1);
function my_assert_handler($file, $line, $code)
{
echo "<hr>Assertion Failed:
File '$file'<br />
Line '$line'<br />
Code '$code'<br /><hr />";
}
assert_options(ASSERT_CALLBACK, 'my_assert_handler');
assert('mysql_query("")');
?>
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Krzysztof 'ChanibaL' Bociurko
01-Oct-2007 06:13
Note that func_get_args() should be used carefully and never in a string! For example:
<?php
function asserted_normal($a, $b) {
assert(var_dump(func_get_args()));
}
function asserted_string($a, $b) {
assert('var_dump(func_get_args())');
}
?>
<?php asserted_normal(1,2) ?> prints
array(2) {
[0]=>
int(1)
[1]=>
int(2)
}
but <?php asserted_string(3,4) ?> prints
array(1) {
[0]=>
string(25) "var_dump(func_get_args())"
}
This is because of that the string passed to assert() is being evaled inside assert, and not your function. Also, note that this works correctly, because of the eval scope:
<?php
function asserted_evaled_string($a, $b) {
assert(eval('var_dump(func_get_args())'));
}
asserted_evaled_string(5,6);
?>
array(2) {
[0]=>
int(5)
[1]=>
int(6)
}
(oh, and for simplicity's sake the evaled code doesn't return true, so don't worry that it fails assertion...)
matthew, at teh dot ath dot cx
16-Sep-2007 08:15
Much of the value of assertions comes from the assumption that you can do performance intensive checking for debugging that will not affect the code in production. Breaking the assumption that assertions will not be routinely enabled in production prohibits this usage and is counterproductive.
tom russo at gmail dot com
24-Dec-2006 03:25
hodgman at ali dot com dot au said:
"Assertions should only be enabled during testing/development, and then disabled once your code reaches a production stage."
Assertions should _not_ be turned off in production code. Although it's common to do so, turning off assertions in production is a bad practice.
If your production code fails an assert, YOU WANT TO KNOW ABOUT IT. Asserts are a debugging tool, but you should not stop debugging your code just because it has gone into production.
Many people claim that removing asserts gives a performance benefit. In modern programming languages this simply isn't true. If you were doing an assert on something that is extremely slow/expensive to compute, you might consider turning that assert off. But in practice this really isn't how asserts are used.
There's a good discussion of this issue in the book The Pragmatic Programmer.
mail<at>aaron-mueller.de
13-Sep-2006 10:51
Here is a simple demonstration of Design By Contract with PHP
<?php
assert_options(ASSERT_ACTIVE, 1);
assert_options(ASSERT_WARNING, 0);
assert_options(ASSERT_BAIL, 1);
assert_options(ASSERT_CALLBACK, 'dcb_callback');
function dcb_callback($script, $line, $message) {
echo "<h1>Condition failed!</h1><br />
Script: <strong>$script</strong><br />
Line: <strong>$line</strong><br />
Condition: <br /><pre>$message</pre>";
}
$a = 5;
$b = 'Simple DCB with PHP';
assert('
is_integer($a) &&
($a > 0) &&
($a < 20) &&
is_string($b) &&
(strlen($b) > 5);
');
function combine($a, $b) {
return "Kombined: " . $b . $a;
}
$result = combine($a, $b);
assert('
is_string($result) &&
(strlen($result) > 0);
');
var_dump($result);
?>
hodgman at ali dot com dot au
10-Aug-2006 04:45
I dont agree with gk at proliberty dot com's statements below.
If you are constantly enabling assertions before each assertion, then you are removing the functionality provided by being able to turn off assertions in the first place.
Assertions should only be enabled during testing/development, and then disabled once your code reaches a production stage.
This means you should either leave disabling/enabling assertions up to the INI file, or let the entry point of the script decide.
If you need an assertion to be there in the final copy of the code, then you are using the wrong tool. Assertions are a tool for debugging only.
gk at proliberty dot com
26-Aug-2005 07:35
If you expect your code to be able to work well with other code, then you should not make any assumptions about the current state of assert_options() flags, prior to calling assert(): other code may disable ASSERT_ACTIVE, without you knowing it - this would render assert() useless!
To avoid this, ALWAYS set assert_options() IMMEDIATELY before calling assert(), per the C++ paradigm for assertion usage:
In one C++ source file, you can define and undefine NDEBUG multiple times, each time followed by #include <cassert>, to enable or disable the assert macro multiple times in the same source file.
Here is how I workaround this issue in my PHP code:
//////////////////////////////////////////////////////////////////////
/// phpxAssertHandler_f
//////////////////////////////////////////////////////////////////////
/**
* @desc Handler which also sets up assert options if not being called as handler
Always fatal when assertion fails
Always make sure assertion is enabled
Cannot depend on other code not using assert or using its own assert handler!
USAGE:
// customize error level of assertion (php assert_options() only allows E_WARNING or nothing at all):
phpxAssertHandler_f(E_USER_NOTICE);
// control assertion active state: not dependent on anything another piece of code might do with ASSERT_ACTIVE
$GLOBALS['MY_ASSERT_ACTIVE']=false;
phpxAssertHandler_f(E_USER_NOTICE,$GLOBALS['MY_ASSERT_ACTIVE']);
// use alternate assertion callback function:
// NOTE: pass null as custom options parameter to use default options
// NOTE: pass no values for assert options parameter array elements to use default options
$GLOBALS['MY_ASSERT_ACTIVE']=false;
$GLOBALS['MY_ASSERT_CALLBACK']='myAssertCallback';
phpxAssertHandler_f(
null,
array(
0=>$GLOBALS['MY_ASSERT_ACTIVE'],
3=>$GLOBALS['MY_ASSERT_CALLBACK'],
)
);
* @param mixed = file or options
* @param line
* @param code
* @return void
*/
function phpxAssertHandler_f($file_or_custom_options=null, $line_or_assert_options=null, $code=null){
static $custom_options;
$debug = false;
if (is_null($code)){
// set default assert_options
$assert_options[]=1;//ASSERT_ACTIVE
$assert_options[]=0;//ASSERT_WARNING -
$assert_options[]=0;//ASSERT_QUIET_EVAL
$assert_options[]=__FUNCTION__;//ASSERT_CALLBACK
// set default custom_options
$custom_options[]=E_USER_ERROR;// error level
if (!is_null($line_or_assert_options)){
// assert_options are passed in
if (!is_array($line_or_assert_options)){
$line_or_assert_options=array($line_or_assert_options);
}
foreach ($line_or_assert_options as $i=>$assert_option){
if ($assert_option===true) $assert_option=1;
if ($assert_option===false) $assert_option=0;
$assert_options[$i]=$assert_option;
if($debug) echo ("assert_options[$i]=$assert_option\n");
}
}
if (!is_null($file_or_custom_options)){
// custom_options are passed in
if (!is_array($file_or_custom_options)){
$file_or_custom_options=array($file_or_custom_options);
}
foreach ($file_or_custom_options as $i=>$custom_option){
if ($custom_option===true) $custom_option=1;
if ($custom_option===false) $custom_option=0;
$custom_options[$i]=$custom_option;
if($debug) echo ("custom_options[$i]=$custom_option\n");
}
}
// set assert options
@assert_options (ASSERT_ACTIVE, $assert_options[0]);
@assert_options (ASSERT_WARNING, $assert_options[1]);
@assert_options (ASSERT_QUIET_EVAL, $assert_options[2]);
@assert_options (ASSERT_CALLBACK, $assert_options[3]);
} else {
// we are acting as a callback function
$file = $file_or_custom_options;
$line = $line_or_assert_options;
$msg="ASSERTION FAILED: $code";
phpxErrorHandler_f ($custom_options[0],$msg,$file,$line);
}
}//phpxAssertHandler_f()
nyk at forumone dot com
26-Aug-2002 06:56
Assertion is a useful debugging feature, but for building unit tests and automated regression tests you should seriously consider using the PHPtest in the PEAR archive (http://pear.php.net/package-info.php?pacid=38) that is based on the JUnit framework for Java. There is also another unit testing framework, also based on JUnit and also called PHPunit on SourceForge (http://sourceforge.net/projects/phpunit/). I believe it is an independent effort from that on PEAR.
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assert_options
