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Fast Parameter Parsing API

In PHP 7, a "Fast Parameter Parsing API" was introduced. See RFC.

This API uses inlining to improve applications performance compared with the zend_parse_parameters() function described below.

Parameter parsing functions

Borrowing from Python's example, there is a set of functions that given the string of type specifiers, can parse the input parameters and store the results in the user specified variables. This avoids using IS_* checks and convert_to_* conversions. The functions also check for the appropriate number of parameters, and try to output meaningful error messages.


/* Implemented. */
int zend_parse_parameters(int num_args, char *type_spec, ...);
int zend_parse_parameters_ex(int flags, int num_args, char *type_spec, ...);

The zend_parse_parameters() function takes the number of parameters passed to the extension function, the type specifier string, and the list of pointers to variables to store the results in. The _ex() version also takes 'flags' argument -- current only ZEND_PARSE_PARAMS_QUIET can be used as 'flags' to specify that the function should operate quietly and not output any error messages.

Both functions return SUCCESS or FAILURE depending on the result.

The auto-conversions are performed as necessary. Arrays, objects, and resources cannot be auto-converted.

PHP 5.3 includes a new function (actually implemented as macro):

int zend_parse_parameters_none();

This returns SUCCESS if no argument has been passed to the function, FAILURE otherwise.

PHP 5.5 includes a new function:

int zend_parse_parameter(int flags, int arg_num, zval **arg, const char *spec, ...);

This function behaves like zend_parse_parameters_ex() except that instead of reading the arguments from the stack, it receives a single zval to convert (passed with double indirection). The passed zval may be changed in place as part of the conversion process.

See also Expose zend_parse_arg() as zend_parse_parameter().

Type specifiers

The following list shows the type specifier, its meaning, and the parameter types that need to be passed by address. All passed parameters are set if the PHP parameter is non-optional and untouched if optional and the parameter is not present. The only exception is O where the zend_class_entry* has to be provided on input and is used to verify the PHP parameter is an instance of that class.

a  - array (zval*)
A  - array or object (zval*)
b  - boolean (bool)
C  - class (zend_class_entry*)
d  - double (double)
f  - function or array containing php method call info (returned as
     zend_fcall_info and zend_fcall_info_cache)
h  - array (returned as HashTable*)
H  - array or HASH_OF(object) (returned as HashTable*)
l  - long (zend_long)
n  - long or double (zval*)
o  - object of any type (zval*)
O  - object of specific type given by class entry (zval*, zend_class_entry)
p  - valid path (string without null bytes in the middle) and its length (char*, size_t)
P  - valid path (string without null bytes in the middle) as zend_string (zend_string*)
r  - resource (zval*)
s  - string (with possible null bytes) and its length (char*, size_t)
S  - string (with possible null bytes) as zend_string (zend_string*)
z  - the actual zval (zval*)
*  - variable arguments list (0 or more)
+  - variable arguments list (1 or more)

The following characters also have a meaning in the specifier string:

Note on 64bit compatibility

Please note that since version 7 PHP uses zend_long as integer type and zend_string with size_t as length, so make sure you pass zend_longs to "l" and size_t to strings length (i.e. for "s" you need to pass char * and size_t), not the other way round!

Both mistakes might cause memory corruptions and segfaults:

char *str;
long str_len; /* XXX THIS IS WRONG!! Use size_t instead. */
zend_parse_parameters(ZEND_NUM_ARGS(), "s", &str, &str_len)
int num; /* XXX THIS IS WRONG!! Use zend_long instead. */
zend_parse_parameters(ZEND_NUM_ARGS(), "l", &num)

If you're in doubt, use check_parameters.php script to the parameters and their types (it can be found in ./scripts/dev/ directory of PHP sources):

php ./scripts/dev/check_parameters.php /path/to/your/sources/


/* Gets a long, a string and its length, and a zval */
zend_long l;
char *s;
size_t s_len;
zval *param;
if (zend_parse_parameters(ZEND_NUM_ARGS(), "lsz",
                          &l, &s, &s_len, &param) == FAILURE) {

/* Gets an object of class specified by my_ce, and an optional double. */
zval *obj;
double d = 0.5;
zend_class_entry *my_ce;
if (zend_parse_parameters(ZEND_NUM_ARGS(), "O|d",
                          &obj, my_ce, &d) == FAILURE) {

/* Gets an object or null, and an array.
   If null is passed for object, obj will be set to NULL. */
zval *obj;
zval *arr;
if (zend_parse_parameters(ZEND_NUM_ARGS(), "o!a",
                          &obj, &arr) == FAILURE) {

/* Gets a separated array which can also be null. */
zval *arr;
if (zend_parse_parameters(ZEND_NUM_ARGS(), "a/!",
                          &arr) == FAILURE) {

/* Get either a set of 3 longs or a string. */
zend_long l1, l2, l3;
char *s;
 * The function expects a pointer to a size_t in this case, not a long
 * or any other type. If you specify a type which is larger
 * than a 'size_t', the upper bits might not be initialized
 * properly, leading to random crashes on platforms like
 * Tru64 or Linux/Alpha.
size_t length;

if (zend_parse_parameters_ex(ZEND_PARSE_PARAMS_QUIET, ZEND_NUM_ARGS(),
                             "lll", &l1, &l2, &l3) == SUCCESS) {
    /* manipulate longs */
} else if (zend_parse_parameters_ex(ZEND_PARSE_PARAMS_QUIET, ZEND_NUM_ARGS(),
                                    "s", &s, &length) == SUCCESS) {
    /* manipulate string */
} else {
    /* output error */


/* Function that accepts only varargs (0 or more) */

int i, num_varargs;
zval *varargs = NULL;

if (zend_parse_parameters(ZEND_NUM_ARGS(), "*", &varargs, &num_varargs) == FAILURE) {

for (i = 0; i < num_varargs; i++) {
    /* do something with varargs[i] */

if (varargs) {

/* Function that accepts a string, followed by varargs (1 or more) */

char *str;
size_t str_len;
int i, num_varargs;
zval *varargs = NULL;

if (zend_parse_parameters(ZEND_NUM_ARGS(), "s+", &str, &str_len, &varargs, &num_varargs) == FAILURE) {

for (i = 0; i < num_varargs; i++) {
    /* do something with varargs[i] */

/* Function that takes an array, followed by varargs, and ending with a long */
zend_long num;
zval *array;
int i, num_varargs;
zval *varargs = NULL;

if (zend_parse_parameters(ZEND_NUM_ARGS(), "a*l", &array, &varargs, &num_varargs, &num) == FAILURE) {

for (i = 0; i < num_varargs; i++) {
    /* do something with varargs[i] */

/* Function that doesn't accept any arguments */
if (zend_parse_parameters_none() == FAILURE) {