Simply talk about the strlen function in PHP

Description of the Strlen function.

int strlen (String $string)

In this article, we can know that the strlen function is defined by the Zend engine. The definition of a function can be viewed here.

The source code for the function is also given here:

Zend_function (strlen) {  char *s1;  int S1_len;  if (Zend_parse_parameters (Zend_num_args () tsrmls_cc, "s", &s1, &s1_len) = = FAILURE) {    return;  }  Retval_long (S1_len);}

The article says that the function is simple and does not require further explanation. This article also has an introduction to the Zend_parse_parameters function. I am more stupid, so I would like to understand how the Zend_parse_parameters function returns the length of the variable.

In the Zend_parse_arg_impl function, where the arguments are parsed, we continue to look at the branch of case ' s '. This branch is the parsing of string variables.

int *PL = Va_arg (*va, int *); is the definition of the string length variable.

Continue looking down, you can see the assignment statement for the PL variable: *pl = z_strlen_pp (arg);.

The Z_STRLEN_PP macro is defined in the Zend_operators.h file:

#define Z_STRLEN_PP (ZVAL_PP) Z_strlen (**ZVAL_PP)

Continue looking at the definition of Z_strlen macro, #define Z_strlen (Zval) (zval). Value.str.len. From this we can know that the strlen function is implemented by directly returning the Len attribute of str in the Zval struct.

The above introduces a simple talk about PHP strlen function, including the aspects of the content, I hope that the PHP tutorial interested in a friend helpful.

