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)