此函数strrpos从字符串的末尾开始查找所需要查找的字符。其他内部实现和strpos差不多是一样的。
/* {{{ proto int strrpos(string haystack, string needle [, int offset]) Finds position of last occurrence of a string within another string */
PHP_FUNCTION(strrpos)
{
zval *zneedle;
char *needle, *haystack;
int needle_len, haystack_len;
long offset = 0;
char *p, *e, ord_needle[2];
if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "sz|l", &haystack, &haystack_len, &zneedle, &offset) == FAILURE) {
RETURN_FALSE;
}
if (Z_TYPE_P(zneedle) == IS_STRING) {
needle = Z_STRVAL_P(zneedle);
needle_len = Z_STRLEN_P(zneedle);
} else {
if (php_needle_char(zneedle, ord_needle TSRMLS_CC) != SUCCESS) {
RETURN_FALSE;
}
ord_needle[1] = '\0';
needle = ord_needle;
needle_len = 1;
}
if ((haystack_len == 0) || (needle_len == 0)) {
RETURN_FALSE;
}
if (offset >= 0) {
if (offset > haystack_len) {
php_error_docref(NULL TSRMLS_CC, E_WARNING, "Offset is greater than the length of haystack string");
RETURN_FALSE;
}
p = haystack + offset;
e = haystack + haystack_len - needle_len;
} else {
if (offset < -INT_MAX || -offset > haystack_len) {
php_error_docref(NULL TSRMLS_CC, E_WARNING, "Offset is greater than the length of haystack string");
RETURN_FALSE;
}
p = haystack;
if (needle_len > -offset) {
e = haystack + haystack_len - needle_len;
} else {
e = haystack + haystack_len + offset;
}
}
if (needle_len == 1) {
/* Single character search can shortcut memcmps */
while (e >= p) {
if (*e == *needle) {
RETURN_LONG(e - p + (offset > 0 ? offset : 0));
}
e--;
}
RETURN_FALSE;
}
while (e >= p) {
if (memcmp(e, needle, needle_len) == 0) {
RETURN_LONG(e - p + (offset > 0 ? offset : 0));
}
e--;
}
RETURN_FALSE;
}
)