assert
(PHP 4, PHP 5, PHP 7, PHP 8)
assert — Checks an assertion
Description
Assertions can be used to aid debugging.
One use case for them is to act as sanity-checks for preconditions
that should always be true and that if they aren't upheld this indicates
some programming errors.
Another use case is to ensure the presence of certain features like
extension functions or certain system limits and features.
As assertions can be configured to be eliminated, they should
not be used for normal runtime operations like
input parameter checks. As a rule of thumb code should behave as expected
even if assertion checking is deactivated.
assert() will check that the expectation given in
assertion holds.
If not, and thus the result is false, it will take the appropriate action
depending on how assert() was configured.
The behaviour of assert() is dictated by the
following INI settings:
Assert Configure Options
| Name |
Default |
Description |
Changelog |
| 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.active |
true |
If false, assert() does not check the expectation
and returns true, unconditionally.
|
Deprecated as of PHP 8.3.0.
|
| assert.callback |
null |
A user defined function to call when an assertion fails.
Its signature should be:
|
Prior to PHP 8.0.0, the signature of the callback should be:
Deprecated as of PHP 8.3.0.
|
| assert.exception |
true |
If true will throw an AssertionError if the
expectation isn't upheld.
|
Deprecated as of PHP 8.3.0.
|
| assert.bail |
false |
If true will abort execution of the PHP script if the
expectation isn't upheld.
|
Deprecated as of PHP 8.3.0.
|
| assert.warning |
true |
If true, will emit an E_WARNING if the
expectation isn't upheld. This INI setting is ineffective if
assert.exception
is enabled.
|
Deprecated as of PHP 8.3.0.
|
Parameters
assertion-
This is any expression that returns a value, which will be executed
and the result is used to indicate whether the assertion succeeded or failed.
Warning
Prior to PHP 8.0.0, if assertion was a
string it was interpreted as PHP code and executed via
eval().
This string would be passed to the callback as the third argument.
This behaviour was DEPRECATED in PHP 7.2.0,
and REMOVED in PHP 8.0.0.
description-
If description is an instance of
Throwable, it will be thrown only if the
assertion is executed and fails.
Note:
As of PHP 8.0.0, this is done prior to calling
the potentially defined assertion callback.
Note:
As of PHP 8.0.0, the object will be thrown regardless of the configuration of
assert.exception.
Note:
As of PHP 8.0.0, the
assert.bail
setting has no effect in this case.
If description is a string this message
will be used if an exception or a warning is emitted.
An optional description that will be included in the failure message if
the assertion fails.
If description is omitted.
A default description equal to the source code for the invocation of
assert() is created at compile time.
Return Values
assert() will always return true if at least one of the following is true:
zend.assertions=0zend.assertions=-1assert.active=0assert.exception=1assert.bail=1- A custom exception object is passed to
description.
If none of the conditions are true assert() will return true if
assertion is truthy and false otherwise.
Examples
Example #1 assert() example
<?php
assert(1 > 2);
echo 'Hi!';
If assertions are enabled (zend.assertions=1)
the above example will output:
Fatal error: Uncaught AssertionError: assert(1 > 2) in example.php:2
Stack trace:
#0 example.php(2): assert(false, 'assert(1 > 2)')
#1 {main}
thrown in example.php on line 2
If assertions are disabled (zend.assertions=0 or zend.assertions=-1)
the above example will output:
Example #2 Using a custom message
<?php
assert(1 > 2, "Expected one to be greater than two");
echo 'Hi!';
If assertions are enabled the above example will output:
Fatal error: Uncaught AssertionError: Expected one to be greater than two in example.php:2
Stack trace:
#0 example.php(2): assert(false, 'Expected one to...')
#1 {main}
thrown in example.php on line 2
If assertions are disabled the above example will output:
Example #3 Using a custom exception class
<?php
class ArithmeticAssertionError extends AssertionError {}
assert(1 > 2, new ArithmeticAssertionError("Expected one to be greater than two"));
echo 'Hi!';
If assertions are enabled the above example will output:
Fatal error: Uncaught ArithmeticAssertionError: Expected one to be greater than two in example.php:4
Stack trace:
#0 {main}
thrown in example.php on line 4
If assertions are disabled the above example will output:
