PHP kernel analysis (8) - zend_compile

Abstract: The php version read here is PHP-7.1.0 RC3, and the platform for reading the code is linux. Go back to the zend_eval_stringlZEND_API that we read before int zend_eval_stringl(char *str, size_t str_len, zval *retval_ptr, char *string_name) /* {{ { */ { ... new_o ...

The php version read here is PHP-7.1.0 RC3, and the platform for reading the code is linux

Go back to the zend_eval_stringl we looked at before

01    ZEND_API int zend_eval_stringl(char *str, size_t str_len, zval *retval_ptr, char *string_name) /* {{{ */    
02    {    
03        ...    
04        new_op_array = zend_compile_string(&pv, string_name);  // 这个是把php代码编译成为opcode的过程    
05        ...    
06        zend_execute(new_op_array, &local_retval); // 这个是具体的执行过程，执行opcode，把结果存储到local_retval中    
07        ...    
08        retval = SUCCESS;    
09        return retval;    
10    }

The zend_execute here performs two steps , the first step is the process of compiling and parsing php into opcode, we will look at this first.

zend_compile_string

zend_compile_string function can be traced to compile_string

01    // 将一个字符串解析成为op_array    
02    zend_op_array *compile_string(zval *source_string, char *filename)    
03    {    
04         zend_lex_state original_lex_state;    
05         zend_op_array *op_array = NULL;    
06         zval tmp;    
07    
08        // 如果传进来要解析的字符为空，则返回null    
09         if (Z_STRLEN_P(source_string)==0) {    
10              return NULL;    
11         }    
12    
13         ZVAL_DUP(&tmp, source_string); // 复制source_string到zval中    
14         convert_to_string(&tmp); // 如果不是字符类型就转换为字符类型    
15         source_string = &tmp;    
16    
17         zend_save_lexical_state(&original_lex_state); // 保存lex上下文    
18         if (zend_prepare_string_for_scanning(source_string, filename) == SUCCESS) {  // 做编译前的准备    
19              BEGIN(ST_IN_SCRIPTING); // 设置状态为正在编译    
20              op_array = zend_compile(ZEND_EVAL_CODE); // 进行编译，并把生成结果放在op_array中    
21         }    
22    
23         zend_restore_lexical_state(&original_lex_state); // 恢复lex上下文    
24         zval_dtor(&tmp); // 释放tmp    
25    
26         return op_array;    
27    }

The core one is zend_compile. Here are a few points to look at:

1 To do type conversion, refer to convert_to_string. This function is to convert any type of value into the string type of zval.
2 zval_dtor, this function can recycle any zval variable. perfectly worked.
3 ZVAL_DUP is for copying. The difference between it and ZVAL_COPY is whether to increase the reference count of gc.

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