How are PHP's built-in functions implemented internally? - php

Question

are these functions written the same way as user functions? I mean with PHP code and with regular expressions and stuff like that?
For example:
filter_var($email, FILTER_VALIDATE_EMAIL);
vs.
http://www.totallyphp.co.uk/code/validate_an_email_address_using_regular_expressions.htm

Answer 1

PHP is written in C. The PHP functions are written in high quality C code then compiled to form the PHP langugae library
if you want to extend PHP (edit / write) own functions check this out: http://www.php.net/~wez/extending-php.pdf
EDIT:
here you go :
This is the original C code for the function:
/* {{{ proto mixed filter_var(mixed variable [, long filter [, mixed options]])
* Returns the filtered version of the vriable.
*/
PHP_FUNCTION(filter_var)
{
long filter = FILTER_DEFAULT;
zval **filter_args = NULL, *data;
if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "z/|lZ", &data, &filter, &filter_args) == FAILURE) {
return;
}
if (!PHP_FILTER_ID_EXISTS(filter)) {
RETURN_FALSE;
}
MAKE_COPY_ZVAL(&data, return_value);
php_filter_call(&return_value, filter, filter_args, 1, FILTER_REQUIRE_SCALAR TSRMLS_CC);
}
/* }}} */
static void php_filter_call(zval **filtered, long filter, zval **filter_args, const int copy, long filter_flags TSRMLS_DC) /* {{{ */
{
zval *options = NULL;
zval **option;
char *charset = NULL;
if (filter_args && Z_TYPE_PP(filter_args) != IS_ARRAY) {
long lval;
PHP_FILTER_GET_LONG_OPT(filter_args, lval);
if (filter != -1) { /* handler for array apply */
/* filter_args is the filter_flags */
filter_flags = lval;
if (!(filter_flags & FILTER_REQUIRE_ARRAY || filter_flags & FILTER_FORCE_ARRAY)) {
filter_flags |= FILTER_REQUIRE_SCALAR;
}
} else {
filter = lval;
}
} else if (filter_args) {
if (zend_hash_find(HASH_OF(*filter_args), "filter", sizeof("filter"), (void **)&option) == SUCCESS) {
PHP_FILTER_GET_LONG_OPT(option, filter);
}
if (zend_hash_find(HASH_OF(*filter_args), "flags", sizeof("flags"), (void **)&option) == SUCCESS) {
PHP_FILTER_GET_LONG_OPT(option, filter_flags);
if (!(filter_flags & FILTER_REQUIRE_ARRAY || filter_flags & FILTER_FORCE_ARRAY)) {
filter_flags |= FILTER_REQUIRE_SCALAR;
}
}
if (zend_hash_find(HASH_OF(*filter_args), "options", sizeof("options"), (void **)&option) == SUCCESS) {
if (filter != FILTER_CALLBACK) {
if (Z_TYPE_PP(option) == IS_ARRAY) {
options = *option;
}
} else {
options = *option;
filter_flags = 0;
}
}
}
if (Z_TYPE_PP(filtered) == IS_ARRAY) {
if (filter_flags & FILTER_REQUIRE_SCALAR) {
if (copy) {
SEPARATE_ZVAL(filtered);
}
zval_dtor(*filtered);
if (filter_flags & FILTER_NULL_ON_FAILURE) {
ZVAL_NULL(*filtered);
} else {
ZVAL_FALSE(*filtered);
}
return;
}
php_zval_filter_recursive(filtered, filter, filter_flags, options, charset, copy TSRMLS_CC);
return;
}
if (filter_flags & FILTER_REQUIRE_ARRAY) {
if (copy) {
SEPARATE_ZVAL(filtered);
}
zval_dtor(*filtered);
if (filter_flags & FILTER_NULL_ON_FAILURE) {
ZVAL_NULL(*filtered);
} else {
ZVAL_FALSE(*filtered);
}
return;
}
php_zval_filter(filtered, filter, filter_flags, options, charset, copy TSRMLS_CC);
if (filter_flags & FILTER_FORCE_ARRAY) {
zval *tmp;
ALLOC_ZVAL(tmp);
MAKE_COPY_ZVAL(filtered, tmp);
zval_dtor(*filtered);
array_init(*filtered);
add_next_index_zval(*filtered, tmp);
}
}
AND HERE IS YOUR VALIDATE EMAIL ROUTINE:
-- this answers your question. Yes, it is done by regex internally.
void php_filter_validate_email(PHP_INPUT_FILTER_PARAM_DECL) /* {{{ */
{
/*
* The regex below is based on a regex by Michael Rushton.
* However, it is not identical. I changed it to only consider routeable
* addresses as valid. Michael's regex considers a#b a valid address
* which conflicts with section 2.3.5 of RFC 5321 which states that:
*
* Only resolvable, fully-qualified domain names (FQDNs) are permitted
* when domain names are used in SMTP. In other words, names that can
* be resolved to MX RRs or address (i.e., A or AAAA) RRs (as discussed
* in Section 5) are permitted, as are CNAME RRs whose targets can be
* resolved, in turn, to MX or address RRs. Local nicknames or
* unqualified names MUST NOT be used.
*
* This regex does not handle comments and folding whitespace. While
* this is technically valid in an email address, these parts aren't
* actually part of the address itself.
*
* Michael's regex carries this copyright:
*
* Copyright © Michael Rushton 2009-10
* http://squiloople.com/
* Feel free to use and redistribute this code. But please keep this copyright notice.
*
*/
const char regexp[] = "/^(?!(?:(?:\\x22?\\x5C[\\x00-\\x7E]\\x22?)|(?:\\x22?[^\\x5C\\x22]\\x22?)){255,})(?!(?:(?:\\x22?\\x5C[\\x00-\\x7E]\\x22?)|(?:\\x22?[^\\x5C\\x22]\\x22?)){65,}#)(?:(?:[\\x21\\x23-\\x27\\x2A\\x2B\\x2D\\x2F-\\x39\\x3D\\x3F\\x5E-\\x7E]+)|(?:\\x22(?:[\\x01-\\x08\\x0B\\x0C\\x0E-\\x1F\\x21\\x23-\\x5B\\x5D-\\x7F]|(?:\\x5C[\\x00-\\x7F]))*\\x22))(?:\\.(?:(?:[\\x21\\x23-\\x27\\x2A\\x2B\\x2D\\x2F-\\x39\\x3D\\x3F\\x5E-\\x7E]+)|(?:\\x22(?:[\\x01-\\x08\\x0B\\x0C\\x0E-\\x1F\\x21\\x23-\\x5B\\x5D-\\x7F]|(?:\\x5C[\\x00-\\x7F]))*\\x22)))*#(?:(?:(?!.*[^.]{64,})(?:(?:(?:xn--)?[a-z0-9]+(?:-[a-z0-9]+)*\\.){1,126}){1,}(?:(?:[a-z][a-z0-9]*)|(?:(?:xn--)[a-z0-9]+))(?:-[a-z0-9]+)*)|(?:\\[(?:(?:IPv6:(?:(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){7})|(?:(?!(?:.*[a-f0-9][:\\]]){7,})(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,5})?::(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,5})?)))|(?:(?:IPv6:(?:(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){5}:)|(?:(?!(?:.*[a-f0-9]:){5,})(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,3})?::(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,3}:)?)))?(?:(?:25[0-5])|(?:2[0-4][0-9])|(?:1[0-9]{2})|(?:[1-9]?[0-9]))(?:\\.(?:(?:25[0-5])|(?:2[0-4][0-9])|(?:1[0-9]{2})|(?:[1-9]?[0-9]))){3}))\\]))$/iD";
pcre *re = NULL;
pcre_extra *pcre_extra = NULL;
int preg_options = 0;
int ovector[150]; /* Needs to be a multiple of 3 */
int matches;
/* The maximum length of an e-mail address is 320 octets, per RFC 2821. */
if (Z_STRLEN_P(value) > 320) {
RETURN_VALIDATION_FAILED
}
re = pcre_get_compiled_regex((char *)regexp, &pcre_extra, &preg_options TSRMLS_CC);
if (!re) {
RETURN_VALIDATION_FAILED
}
matches = pcre_exec(re, NULL, Z_STRVAL_P(value), Z_STRLEN_P(value), 0, 0, ovector, 3);
/* 0 means that the vector is too small to hold all the captured substring offsets */
if (matches < 0) {
RETURN_VALIDATION_FAILED
}
}
/* }}} */

Answer 2

PHP functions are either :
Written in C -- and not in PHP
Or just wrappers to functions provided by other libraries (For instance, PHP's curl extension is just a wrapper arround the curl library).
If you are curious, you can take a look at the sources of PHP -- here's its SVN : http://svn.php.net/viewvc/
For instance, the filter_var() function should be defined somewhere in the sources of the filter extension.

Answer 3

Nope. PHP-internal functions are written in C, not with PHP code. Which looks quite unwieldy due to the many Zend-runtime macros and how parameters are transferred from PHP into C structures.
That particular function does use a regular expression. It also makes a nice example:
http://svn.php.net/repository/php/php-src/branches/PHP_5_3/ext/filter/logical_filters.c
Look for regexp[] somewhere in the middle.