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;

}