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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