if(substr(php_sapi_name(),0,6)=='cli'){
    //命令行模式

    global $argv;
    $function = $argv[1];
}else{
       //网页方式

       $function = $_GET['name'];
}
$extensions = get_loaded_extensions();
foreach($extensions as $t){
    $modules_funcs = get_extension_funcs($t);
    if(in_array($function, (array)$modules_funcs)){
        $is_found = true;
        echo "$function is in $t module\n";
    }
}
if(!$is_found)echo "$function not found";

?>

if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "sz|l", &haystack, &haystack_len, &needle, &offset) == FAILURE) {
        return;
    }
        检查参数，第一第二个是必选参数，第三个是可选，|表示后面的参数都是可选的。

if (offset < 0 || offset > haystack_len) {
        php_error_docref(NULL TSRMLS_CC, E_WARNING, "Offset not contained in string");
        RETURN_FALSE;
    }

if (haystack_len == 0) {
        RETURN_FALSE;
    }

haystack_dup = estrndup(haystack, haystack_len);
        //与大小写无关,所以先把字符全部转换成小写

php_strtolower(haystack_dup, haystack_len);

if (Z_TYPE_P(needle) == IS_STRING) {
               //第二个参数如果是字符串

if (Z_STRLEN_P(needle) == 0 || Z_STRLEN_P(needle) > haystack_len) {
            efree(haystack_dup);
            RETURN_FALSE;
        }

needle_dup = estrndup(Z_STRVAL_P(needle), Z_STRLEN_P(needle));
        php_strtolower(needle_dup, Z_STRLEN_P(needle));
                //这个是关键,由php_memnstr实现

found = php_memnstr(haystack_dup + offset, needle_dup, Z_STRLEN_P(needle), haystack_dup + haystack_len);
    } else {
               //第二个参数是数字的话,则强制转换成(char)类型

switch (Z_TYPE_P(needle)) {
            case IS_LONG:
            case IS_BOOL:
                needle_char[0] = tolower((char) Z_LVAL_P(needle));
                break;
            case IS_DOUBLE:
                needle_char[0] = tolower((char) Z_DVAL_P(needle));
                break;
            default:
                php_error_docref(NULL TSRMLS_CC, E_WARNING, "needle is not a string or an integer");
                efree(haystack_dup);
                RETURN_FALSE;
                break;

}
        needle_char[1] = '\0';
        found = php_memnstr(haystack_dup + offset,
                            needle_char,
                            sizeof(needle_char) - 1,
                            haystack_dup + haystack_len);
    }

efree(haystack_dup);
    if (needle_dup) {
        efree(needle_dup);
    }

if (found) {
                //如何找到,则返回在这个字符串中的位置

RETURN_LONG(found - haystack_dup);
    } else {
        RETURN_FALSE;
    }
}

end -= needle_len;

while (p <= end) {
        if ((p = (char *)memchr(p, *needle, (end-p+1))) && ne == p[needle_len-1]) {
            if (!memcmp(needle, p, needle_len-1)) {
                return p;
            }
        }

if (p == NULL) {
            return NULL;
        }

p++;
    }

return NULL;
}