You can call user functions from your own modules, which is very
handy when implementing callbacks; for example, for array walking, searching, or
simply for event-based programs.
User functions can be called with the
function call_user_function_ex(). It requires a hash value
for the function table you want to access, a pointer to an object (if you want
to call a method), the function name, return value, number of arguments,
argument array, and a flag indicating whether you want to perform zval separation.
ZEND_API int call_user_function_ex(HashTable *function_table, zval *object,
zval *function_name, zval **retval_ptr_ptr,
int param_count, zval **params,
Note that you don't have to specify both
function_table and object; either
will do. If you want to call a method, you have to supply the
object that contains this method, in which case
call_user_function()automatically sets the
function table to this object's function table. Otherwise, you only
need to specify function_table and can set
object to NULL.
Usually, the default function table is the "root" function table
containing all function entries. This function table is part of the
compiler globals and can be accessed using the macro
CG. To introduce the compiler globals to your
function, call the macro TSRMLS_FETCH once.
The function name is specified in a zval
container. This might be a bit surprising at first, but is quite a
logical step, since most of the time you'll accept function names
as parameters from calling functions within your script, which in
turn are contained in zval containers again. Thus,
you only have to pass your arguments through to this function. This
zval must be of type IS_STRING.
The next argument consists of a pointer to the return value. You
don't have to allocate memory for this container; the function will
do so by itself. However, you have to destroy this container (using
Next is the parameter count as integer and an array containing all
necessary parameters. The last argument specifies whether the
function should perform zval separation - this should always be set
to 0. If set to 1, the
function consumes less memory but fails if any of the parameters
Example 58-1 shows a small demonstration of
calling a user function. The code calls a function that's supplied
to it as argument and directly passes this function's return value
through as its own return value. Note the use of the constructor
and destructor calls at the end - it might not be necessary to do
it this way here (since they should be separate values, the
assignment might be safe), but this is bulletproof.
Example 58-1. Calling user functions.
if((ZEND_NUM_ARGS() != 1) || (zend_get_parameters_ex(1, &function_name) != SUCCESS))
if((*function_name)->type != IS_STRING)
zend_error(E_ERROR, "Function requires string argument");
if(call_user_function_ex(CG(function_table), NULL, *function_name, &retval, 0, NULL, 0) != SUCCESS)
zend_error(E_ERROR, "Function call failed");
zend_printf("We have %i as type<br>", retval->type);
*return_value = *retval;
print("We are in the test function!<br>");
$return_value = call_userland("test_function");
print("Return value: \"$return_value\"<br>");