[PHP Source reading note]strlen function

Article from: Http://www.aintnot.com/2016/02/22/phps-source-analytics-strlen

Description of the Strlen function.

strlen string $string )

In this article, we can know that strlen the 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 " s ", &s1, &s1_len) = = FAILURE)        {return;    }    Retval_long (S1_len);}

The article says that the function is simple and does not require further explanation. And this article also has the zend_parse_parameters function to do the introduction. I am more stupid, so I want to understand zend_parse_parameters how the function returns the length of the variable.

In the zend_parse_arg_impl function, which is where the argument is parsed, we continue to look at case ‘s‘ the branch. This branch is the parsing of string variables.

int *pl = va_arg(*va, int *);Is the definition of a string length variable.

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

and the Z_STRLEN_PP definition of the macro in the zend_operators.h file:

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

Then continue to see Z_STRLEN the definition of the 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.

[PHP Source reading note]strlen function