PHP function substring replacement str_replace_PHP tutorial

As above, start with the characters "#" is replaced with the character "-" at the beginning.

Preparatory work:

Download the PHP source code, download it from http://www.php.net
Create your own code reading tool [I use VIM+CSCOPE] Also : Linux users also recommend the graphical source code viewing tool kscope [google]

/* }}} */


Now you need to view the function php_str_replace_common function



Copy code

The code is as follows:

/* {{{ 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, "ZZZ|Z", &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);
}
}
/* }}} */

继续跟踪php_str_replace_in_subject

到现在为止，我们的目标最终锁定到了php_char_to_str_ex 函数，现在只需要分析这个函数就OK了。其实现为：

As commented above, this completes the replacement of characters into strings. As for how to return and the detailed process, you need to have a relative understanding of the PHP execution process.
Of course, you can use gdb to set a breakpoint to the php_char_to_str_ex function to understand its detailed execution process.
The next article will be about the analysis of replacing strings with strings.
Summary:
The result is stored in zval
The implementation of replacement is quite clever and can be learned.
You need to continue to view the source code and learn more writing skills and design skills.