str_replace — 子字符串替换 [str_replace]
mixed str_replace ( mixed $search , mixed $replace , mixed $subject [, int &$count ] )
php函数str_replace: 返回一个字符串或者数组。该字符串或数组是将 subject 中全部的 search 都被 replace 替换之后的结果。
现在我们所能知道的一些这个函数的用法，如：str_replace("#", "-", "dizaz#7#final")，str_replace(array('#', '$'), "-", "dizaz#7$final") 等，就这些调用方式，php内部是如何实现的呢，鉴于[深入理解PHP内核]，在这里小做分析。
测试代码：
复制代码 代码如下:
$object = "dizaz#7#final";
$res = str_replace("#", "-", $object);
echo $res;
复制代码 代码如下:
/* {{{ proto mixed str_replace(mixed search, mixed replace, mixed subject [, int &replace_count])
Replaces all occurrences of search in haystack with replace */
PHP_FUNCTION(str_replace)
{
php_str_replace_common(INTERNAL_FUNCTION_PARAM_PASSTHRU, 1);
}
/* }}} */
复制代码 代码如下:
/* {{{ php_str_replace_common
*/
static void php_str_replace_common(INTERNAL_FUNCTION_PARAMETERS, int case_sensitivity)
{
/**
* TODO
* typedef struct _zval_struct zval;
* typedef struct _zend_class_entry zend_class_entry
*
* struct _zval_struct {
* zvalue_value value;
* zend_uint refcount__gc;
* zend_uchar type;
* zend_uchar is_ref__gc;
* };
*
* typedef union _zvalue_value {
* long lval;
* double dval;
* struct {
* char *val;
* int len;
* } str;
* HashTable *ht;
* zend_object_value obj;
* } zvalue_value;
*
* typedef struct _zend_object {
* zend_class_entry *ce;
* HashTable *properties;
* HashTable *guards;
* } zend_object;
*
*/
zval **subject, **search, **replace, **subject_entry, **zcount = NULL;
zval *result;
char *string_key;
uint string_key_len;
ulong num_key;
int count = 0;
int argc = ZEND_NUM_ARGS();
if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "ZZZZ", &search, &replace, &subject, &zcount) == FAILURE) {
return;
}
SEPARATE_ZVAL(search);
SEPARATE_ZVAL(replace);
SEPARATE_ZVAL(subject);
/* Make sure we're dealing with strings and do the replacement. */
if (Z_TYPE_PP(search) != IS_ARRAY) {
....//代码省滤
} else { /* if subject is not an array */
php_str_replace_in_subject(*search, *replace, subject, return_value, case_sensitivity, (argc > 3) ? &count : NULL);
}
if (argc > 3) {
zval_dtor(*zcount);
ZVAL_LONG(*zcount, count);
}
}
/* }}} */
复制代码 代码如下:
/* {{{ php_str_replace_in_subject
*/
static void php_str_replace_in_subject(zval *search, zval *replace, zval **subject, zval *result, int case_sensitivity, int *replace_count)
{
zval **search_entry,
**replace_entry = NULL,
temp_result;
char *replace_value = NULL;
int replace_len = 0;
/* Make sure we're dealing with strings. */
convert_to_string_ex(subject);
Z_TYPE_P(result) = IS_STRING;
if (Z_STRLEN_PP(subject) == 0) {
ZVAL_STRINGL(result, "", 0, 1);
return;
}
/* If search is an array */
if (Z_TYPE_P(search) == IS_ARRAY) {
...//不走这步
} else {
if (Z_STRLEN_P(search) == 1) { //例子中只有”#“所以，执行这一步。
php_char_to_str_ex(Z_STRVAL_PP(subject),//subject的值，也就是dizaz#7#final
Z_STRLEN_PP(subject), //获取subject的长度
Z_STRVAL_P(search)[0], //由于只有1个”#”，所以只需要第一个字符
Z_STRVAL_P(replace), //所要替换成的字符，现在是“-”
Z_STRLEN_P(replace), //目标字符的长度，现在为1
result, //替换结果
case_sensitivity, //大小写是否敏感，默认是1
replace_count); //替换次数
} else if (Z_STRLEN_P(search) > 1) {
Z_STRVAL_P(result) = php_str_to_str_ex(Z_STRVAL_PP(subject), Z_STRLEN_PP(subject),
Z_STRVAL_P(search), Z_STRLEN_P(search),
Z_STRVAL_P(replace), Z_STRLEN_P(replace), &Z_STRLEN_P(result), case_sensitivity, replace_count);
} else {
MAKE_COPY_ZVAL(subject, result);
}
}
}
复制代码 代码如下:
/* {{{ php_char_to_str_ex
*/
PHPAPI int php_char_to_str_ex(char *str, uint len, char from, char *to, int to_len, zval *result, int case_sensitivity, int *replace_count)
{
int char_count = 0;
int replaced = 0;
char *source, *target, *tmp, *source_end=str+len, *tmp_end = NULL;
if (case_sensitivity) { //现在case_sensitivity = 1
char *p = str, *e = p + len;
//计算需要替换几次
while ((p = memchr(p, from, (e - p)))) {
char_count++;
p++;
}
} else {
for (source = str; source if (tolower(*source) == tolower(from)) {
char_count++;
}
}
}
if (char_count == 0 && case_sensitivity) {
ZVAL_STRINGL(result, str, len, 1);
return 0;
}
//计算替换以后的长度，并且存储到result中。
Z_STRLEN_P(result) = len + (char_count * (to_len - 1));
//申请内存，存放替换后的数据
Z_STRVAL_P(result) = target = safe_emalloc(char_count, to_len, len + 1);
//设定结果是一个字符串
Z_TYPE_P(result) = IS_STRING;
//target跟result的值都指向统一块内存，所以只需要处理target
if (case_sensitivity) {
char *p = str, *e = p + len, *s = str;
while ((p = memchr(p, from, (e - p)))) { //判断在第几个字符出现#
memcpy(target, s, (p - s)); //把#以前的数据拷贝给target
target += p - s;
memcpy(target, to, to_len); //把目标字符拷贝给target[当然此时的target是开始target+p-s的]
target += to_len;
p++;
s = p;
if (replace_count) {
*replace_count += 1; //设定替换次数
}
}
//如果后面还有，继续添加到target后，这样target所指向的内存块已经是替换好的数据了。
if (s memcpy(target, s, (e - s));
target += e - s;
}
} else {
for (source = str; source if (tolower(*source) == tolower(from)) {
replaced = 1;
if (replace_count) {
*replace_count += 1;
}
for (tmp = to, tmp_end = tmp+to_len; tmp *target = *tmp;
target++;
}
} else {
*target = *source;
target++;
}
}
}
*target = 0;
return replaced;
}
/* }}} */
