opcode：

通过上图你能获得哪些信息呢？

行号、指令编号、脚本开始标记、结束标记、ZEND VM指令、返回值、ZEND VM指令对应的参数。

ZEND VM执行opcode

struct _zend_op {

    opcode_handler_t handler; // 执行该opcode时调用的处理函数

    znode result;

    znode op1;

    znode op2;

    ulong extended_value;

    uint lineno;

    zend_uchar opcode;  // opcode代码

};

struct _zend_op_array {

/* Common elements */

zend_uchar type;

char *function_name;

zend_class_entry *scope;

zend_uint fn_flags;

union _zend_function *prototype;

zend_uint num_args;

zend_uint required_num_args;

zend_arg_info *arg_info;

zend_bool pass_rest_by_reference;

unsigned char return_reference;

/* END of common elements */

zend_bool done_pass_two;

zend_uint *refcount;

zend_op *opcodes;

zend_uint last, size;

zend_compiled_variable *vars;

int last_var, size_var;

zend_uint T;

zend_brk_cont_element *brk_cont_array;

int last_brk_cont;

int current_brk_cont;

zend_try_catch_element *try_catch_array;

int last_try_catch;

/* static variables support */

HashTable *static_variables;

zend_op *start_op;

int backpatch_count;

zend_uint this_var;

char *filename;

zend_uint line_start;

zend_uint line_end;

char *doc_comment;

zend_uint doc_comment_len;

zend_uint early_binding; /* the linked list of delayed declarations */

void *reserved[ZEND_MAX_RESERVED_RESOURCES];

};

ZEND_API void execute(zend_op_array *op_array TSRMLS_DC)

{

    // ... 循环执行op_array中的opcode或者执行其他op_array中的opcode

}

实际上我们编写的PHP，最终解析成ZEND VM中的指令集，最终通过ZEND VM返回结果。

每一条指令，都可以找到对用的函数执行，例如ECHO指令对应zend_do_echo。更多的可以查看Zend/compile.h