#define ZEND_INTERNAL_FUNCTION              1
#define ZEND_USER_FUNCTION                  2
#define ZEND_OVERLOADED_FUNCTION            3
#define ZEND_EVAL_CODE                      4
#define ZEND_OVERLOADED_FUNCTION_TEMPORARY  5

struct _zend_execute_data {//...省略部分代码
    zend_function_state function_state;zend_function *fbc; /* Function Being Called *///...省略部分代码
};

typedef struct _zend_function_state {zend_function *function;void **arguments;
} zend_function_state;

typedef union _zend_function {zend_uchar type;    /* MUST be the first element of this struct! */struct {zend_uchar type;  /* never used */char *function_name;    //函数名称zend_class_entry *scope; //函数所在的类作用域zend_uint fn_flags;     //函数类型，如用户自定义则为 #define
ZEND_USER_FUNCTION 2  union _zend_function *prototype; //函数原型zend_uint num_args;     //参数数目zend_uint required_num_args; //需要的参数数目zend_arg_info *arg_info;  //参数信息指针
        zend_bool pass_rest_by_reference;unsigned char return_reference;  //返回值
    } common;zend_op_array op_array;   //函数中的操作
zend_internal_function internal_function;
} zend_function;

typedef struct _zend_internal_function {/* 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 */void (*handler)(INTERNAL_FUNCTION_PARAMETERS);struct _zend_module_entry *module;
} zend_internal_function;

$func = 'print_r';
$func('i am print_r function.');

function name:  (null)
number of ops:  9
compiled vars:  !0 = $func
line     # *  op                           fetch          ext  return operands
------------------------------------------------------------------------------
-
-2     0  >   EXT_STMT1      ASSIGN                                                   !0,
'print_r'3     2      EXT_STMT3      INIT_FCALL_BY_NAME                                       !04      EXT_FCALL_BEGIN5      SEND_VAL
'i+am+print_r+function.'6      DO_FCALL_BY_NAME                              17      EXT_FCALL_END8    > RETURN        　　　　　　　　　　　　　　　　　　　　　　　　　　1

print_r('i am print_r function.');

function name:  (null)
number of ops:  6
compiled vars:  none
line     # *  op                           fetch          ext  return  operands
-------------------------------------------------------------------------------
-
-2     0  >   EXT_STMT1      EXT_FCALL_BEGIN2      SEND_VAL
'i+am+print_r+function.'3      DO_FCALL                                      1
'print_r'4      EXT_FCALL_END5    > RETURN                                                   1

if (!is_method && !is_dynamic_fcall && function_name->op_type==IS_CONST) {opline->opcode = ZEND_DO_FCALL;opline->op1 = *function_name;ZVAL_LONG(&opline->op2.u.constant,
zend_hash_func(Z_STRVAL(function_name->u.constant), Z_STRLEN(function_name-
>u.constant) + 1));} else {opline->opcode = ZEND_DO_FCALL_BY_NAME;SET_UNUSED(opline->op1);}