PHP 5.6.4 is available

assert

(PHP 4, PHP 5)

assert Prüft ab, ob eine Bedingung oder Abfrage FALSE ist

Beschreibung

int assert ( string|bool $assertion )

assert() überprüft den übergebenen Parameter assertion und führt ein über die Funktion assert_options() definiertes Ereignis aus, falls die in assertion spezifizierte Bedingung FALSE ist.

Wird der Parameter assertion als String übergeben, so wird der String als PHP-Code interpretiert. Der Vorteil der Übergabe des Parameters assertion als Zeichenkette liegt darin, dass die ausgegebene Meldung die über assertion übergebene Zeichenkette enthält.

assert() sollte nur zum Debuggen des Codes und nicht in Produktionsumgebungen verwendet werden werden, beispielsweise zur Überprüfung von Eingaben.

Die Optionen für die assert() können über die Funktion assert_options() oder in den Einstellungen der .ini-Datei gesetzt werden.

Die Funktion assert_options() mit der ASSERT_CALLBACK Direktive ermöglicht eine Funktion anzugeben, die bei fehlender Überprüfung aufgerufen wird.

Callback-Funktionen in Zusammenhang mit assert() sind nützlich, um beispielsweise automatisierte Tests durchzuführen, da die Callback-Funktion über die Information verfügt, von welcher Stelle sie aufgerufen wurde.

Die Callback-Funktion wird mit drei Parametern aufgerufen. Der erste Parameter enthält den Namen des Scripts, in dem die Überprüfung statt fand, der zweite Parameter die Zeilennummer, und der dritte Paramter enthält die über assertion angegebene Bedingung.

Beispiel #1 Überprüfung mit benutzerdefinierter Funktion

<?php
// Active assert and make it quiet
assert_options (ASSERT_ACTIVE1);
assert_options (ASSERT_WARNING0);
assert_options (ASSERT_QUIET_EVAL1);

// Create a handler function
function my_assert_handler ($file$line$code) {
    echo 
"<hr>Assertion Failed:
        File '
$file'<br>
        Line '
$line'<br>
        Code '
$code'<br><hr>";
}

// Set up the callback
assert_options (ASSERT_CALLBACK'my_assert_handler');

// Make an assertion that should fail
assert ('mysql_query ("")');
?>

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User Contributed Notes 8 notes

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2
Krzysztof &#39;ChanibaL&#39; Bociurko
7 years ago
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...)
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1
office dot stojmenovic at gmail dot com
1 year ago
Example from Ikac Framework how they use assert()

<?php

   
/**
     * Set Assertion Debug
     *
     * This method will check the given assertion and take appropriate -
     * action if its result is FALSE.
     *
     * This file is part of Ikac Framework.
     *
     * @package Ikac Framework
     * @author Ivan Stojmenovic Ikac <contact.@stojmenovic.info>
     *
     * @param mixed $assertion  The assertion.
     * @param mixed $callback Callback to call on failed assertions
     * @param array $options  Set the various control options or just query their current settings.
     * @param string $description  An optional description that will be included in the failure message if the assertion fails.
     */
   
public function setAssertionDebug($assertion, $callback, array $options, $description = null)
    {
        if (
is_array($options)) {
            foreach (
$options AS $option => $value) {
               
assert_options($option, $value);
            }
        }
        if (
$callback) {
           
assert_options(ASSERT_CALLBACK, $callback);
        }
       
        return
assert($assertion, $description);
    }
   
?>

How to use:

<?php
     
use Ikac\Component\SystemBehaviour\OptionsInfo;

     
$system = new OptionsInfo();

     
$option = array(ASSERT_ACTIVE => 1,ASSERT_WARNING => 0,ASSERT_QUIET_EVAL => 1);

    
$system->setAssertionDebug('2<1', function(){
            echo
"Assertion failed";
     },
$option);

?>
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1
uramihsayibok, gmail, com
4 years ago
There's a nice advantage to giving assert() some code to execute, as a string, rather than a simple true/false value: commenting.

<?php

assert
('is_int($int) /* $int parameter must be an int, not just numeric */');

// and my personal favorite
assert('false /* not yet implemented */');

?>

The comment will show up in the output (or in your assertion handler) and doesn't require someone debugging to go through your code trying to figure out why the assertion happened. That's no excuse to not comment your code, of course.

You need to use a block comment (/*...*/) because a line comment (//...) creates an "unexpected $end" parse error in the evaluated code. Bug? Could be.
(You can get around it with "false // not yet implemented\n" but that screws up the message)
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2
hodgman at ali dot com dot au
6 years ago
As noted on Wikipedia - "assertions are primarily a development tool, they are often disabled when a program is released to the public." and "Assertions should be used to document logically impossible situations and discover programming errors— if the 'impossible' occurs, then something fundamental is clearly wrong. This is distinct from error handling: most error conditions are possible, although some may be extremely unlikely to occur in practice. Using assertions as a general-purpose error handling mechanism is usually unwise: assertions do not allow for graceful recovery from errors, and an assertion failure will often halt the program's execution abruptly. Assertions also do not display a user-friendly error message."

This means that the advice given by "gk at proliberty dot com" to force assertions to be enabled, even when they have been disabled manually, goes against best practices of only using them as a development tool.
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1
devoto13 at gmail dot com
1 year ago
"If you would like to compare with === or !== you need to add '(string)' before string numbers. Or wrap them with quotes."

Do not use this aproach, because it would not work, look at http://php.net/manual/en/function.var-export.php .
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1
mail<at>aaron-mueller.de
8 years ago
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>";
}

// Parameters
$a = 5;
$b = 'Simple DCB with PHP';

// Pre-Condition
assert('
    is_integer($a) &&
    ($a > 0) &&
    ($a < 20) &&
   
    is_string($b) &&
    (strlen($b) > 5);
'
);

// Function
function combine($a, $b) {
    return
"Kombined: " . $b . $a;
}

$result = combine($a, $b);

// Post-Condition
assert('
    is_string($result) &&
    (strlen($result) > 0);
'
);

// All right, the Function works fine
var_dump($result);

?>
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-2
gk at proliberty dot com
9 years ago
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:

<?php
//////////////////////////////////////////////////////////////////////
/// 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()
?>
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-12
fabiano dot fa04 at gmail dot com
1 year ago
You can also use a function instead a string description as the second parameter.

<?php

   
function assertIsFalse(){
        echo
"Hey, this assert is false and I'm a function.";
    }

   
$foo = "foo";
   
$bar = $foo;

   
$foo = "bar";

   
assert( $foo == $bar, assertIsFalse() );

?>

The result would be:

Hey, this assert is false and I'm a function.
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