问 a 等于什么的时候 if 为true

zend_types.h 844行，相当于调用handlers->compare，如何设置这个呢？

#define Z_OBJ(zval)                 (zval).value.obj
#define Z_OBJ_P(zval_p)             Z_OBJ(*(zval_p))

#define Z_OBJ_HT(zval)              Z_OBJ(zval)->handlers
#define Z_OBJ_HT_P(zval_p)          Z_OBJ_HT(*(zval_p))

#define Z_OBJ_HANDLER(zval, hf)     Z_OBJ_HT((zval))->hf 
#define Z_OBJ_HANDLER_P(zv_p, hf)   Z_OBJ_HANDLER(*(zv_p), hf)

相同的文件 288 行，从这里可以找到(zval).value.obj

  typedef union _zend_value {
      zend_long         lval;             /* long value */
      double            dval;             /* double value */
      zend_refcounted  *counted;
      zend_string      *str;
      zend_array       *arr;
      zend_object      *obj;
      zend_resource    *res;
      zend_reference   *ref;
      zend_ast_ref     *ast;
      zval             *zv;
      void             *ptr;
      zend_class_entry *ce;
      zend_function    *func;
      struct {
          uint32_t w1;
          uint32_t w2;
      } ww;
  } zend_value;


  struct _zval_struct {
      zend_value        value;            /* value */
      union {
          uint32_t type_info;
          struct {
              ZEND_ENDIAN_LOHI_3(
                  zend_uchar    type,         /* active type */
                  zend_uchar    type_flags,
                  union {
                      uint16_t  extra;        /* not further specified */
                  } u)
          } v;
      } u1;
      union {
          uint32_t     next;                 /* hash collision chain */
          uint32_t     cache_slot;           /* cache slot (for RECV_INIT) */
          uint32_t     opline_num;           /* opline number (for FAST_CALL) */
          uint32_t     lineno;               /* line number (for ast nodes) */
          uint32_t     num_args;             /* arguments number for EX(This) */
          uint32_t     fe_pos;               /* foreach position */
          uint32_t     fe_iter_idx;          /* foreach iterator index */
          uint32_t     property_guard;       /* single property guard */
          uint32_t     constant_flags;       /* constant flags */
          uint32_t     extra;                /* not further specified */
      } u2;
  };

480行，可以找到handlers

  struct _zend_object {
      zend_refcounted_h gc;
      uint32_t          handle; // TODO: may be removed ???
      zend_class_entry *ce;
      const zend_object_handlers *handlers;
      HashTable        *properties;
      zval              properties_table[1];
  };

文件 zend_object_handlers.h，159行终于找到了compare

  struct _zend_object_handlers {
      /* offset of real object header (usually zero) */
      int                                     offset;
      /* object handlers */
      zend_object_free_obj_t                  free_obj;             /* required */
      zend_object_dtor_obj_t                  dtor_obj;             /* required */
      zend_object_clone_obj_t                 clone_obj;            /* optional */
      zend_object_read_property_t             read_property;        /* required */
      zend_object_write_property_t            write_property;       /* required */
      zend_object_read_dimension_t            read_dimension;       /* required */
      zend_object_write_dimension_t           write_dimension;      /* required */
      zend_object_get_property_ptr_ptr_t      get_property_ptr_ptr; /* required */
      zend_object_has_property_t              has_property;         /* required */
      zend_object_unset_property_t            unset_property;       /* required */
      zend_object_has_dimension_t             has_dimension;        /* required */
      zend_object_unset_dimension_t           unset_dimension;      /* required */
      zend_object_get_properties_t            get_properties;       /* required */
      zend_object_get_method_t                get_method;           /* required */
      zend_object_get_constructor_t           get_constructor;      /* required */
      zend_object_get_class_name_t            get_class_name;       /* required */
      zend_object_cast_t                      cast_object;          /* required */
      zend_object_count_elements_t            count_elements;       /* optional */
      zend_object_get_debug_info_t            get_debug_info;       /* optional */
      zend_object_get_closure_t               get_closure;          /* optional */
      zend_object_get_gc_t                    get_gc;               /* required */
      zend_object_do_operation_t              do_operation;         /* optional */
      zend_object_compare_t                   compare;              /* required */
      zend_object_get_properties_for_t        get_properties_for;   /* optional */
  };

zend_object_handlers.c ，1912行，可以看到标准的compare定义

  ZEND_API const zend_object_handlers std_object_handlers = {      
  0,                                      /* offset */        
  zend_object_std_dtor,                   /* free_obj */     
  zend_objects_destroy_object,            /* dtor_obj */     
  zend_objects_clone_obj,                 /* clone_obj */   
  zend_std_read_property,                 /* read_property */
  zend_std_write_property,                /* write_property */
  zend_std_read_dimension,                /* read_dimension */       
  zend_std_write_dimension,               /* write_dimension */       
  zend_std_get_property_ptr_ptr,          /* get_property_ptr_ptr */       
  zend_std_has_property,                  /* has_property */       
  zend_std_unset_property,                /* unset_property */       
  zend_std_has_dimension,                 /* has_dimension */       
  zend_std_unset_dimension,               /* unset_dimension */       
  zend_std_get_properties,                /* get_properties */       
  zend_std_get_method,                    /* get_method */       
  zend_std_get_constructor,               /* get_constructor */
  zend_std_get_class_name,                /* get_class_name */ 
  zend_std_cast_object_tostring,          /* cast_object */       
  NULL,                                   /* count_elements */       
  zend_std_get_debug_info,                /* get_debug_info */       
  zend_std_get_closure,                   /* get_closure */       
  zend_std_get_gc,                        /* get_gc */       
  NULL,                                   /* do_operation */       
  zend_std_compare_objects,               /* compare */      
  NULL,                                   /* get_properties_for */   
  }; 

相同文件 1580行,没有全部复制完，余下的代码是比较两个不同对象的，用不上。

 ZEND_API int zend_std_compare_objects(zval *o1, zval *o2) /* {{{ */
  {
      zend_object *zobj1, *zobj2;

      if (Z_TYPE_P(o1) != Z_TYPE_P(o2)) {
          /* Object and non-object */
          zval casted;
          if (Z_TYPE_P(o1) == IS_OBJECT) {
              ZEND_ASSERT(Z_TYPE_P(o2) != IS_OBJECT);
              zend_uchar target_type = (Z_TYPE_P(o2) == IS_FALSE || Z_TYPE_P(o2) == IS_TRUE)
                  ? _IS_BOOL : Z_TYPE_P(o2);
              if (Z_OBJ_HT_P(o1)->cast_object(Z_OBJ_P(o1), &casted, target_type) == FAILURE) {
                  // TODO: Less crazy.
                  if (target_type == IS_LONG || target_type == IS_DOUBLE) {
                      zend_error(E_NOTICE, "Object of class %s could not be converted to %s",
                          ZSTR_VAL(Z_OBJCE_P(o1)->name), zend_get_type_by_const(target_type));
                      if (target_type == IS_LONG) {
                          ZVAL_LONG(&casted, 1);
                      } else {
                          ZVAL_DOUBLE(&casted, 1.0);
                      }
                  } else {
                      return 1;
                  }
              }
              int ret = zend_compare(&casted, o2);
              zval_ptr_dtor(&casted);
              return ret;
          } else {
              ZEND_ASSERT(Z_TYPE_P(o2) == IS_OBJECT);
              zend_uchar target_type = (Z_TYPE_P(o1) == IS_FALSE || Z_TYPE_P(o1) == IS_TRUE)
                  ? _IS_BOOL : Z_TYPE_P(o1);
              if (Z_OBJ_HT_P(o2)->cast_object(Z_OBJ_P(o2), &casted, target_type) == FAILURE) {
                  // TODO: Less crazy.
                  if (target_type == IS_LONG || target_type == IS_DOUBLE) {
                      zend_error(E_NOTICE, "Object of class %s could not be converted to %s",
                          ZSTR_VAL(Z_OBJCE_P(o2)->name), zend_get_type_by_const(target_type));
                      if (target_type == IS_LONG) {
                          ZVAL_LONG(&casted, 1);
                      } else {
                          ZVAL_DOUBLE(&casted, 1.0);
                      }
                  } else {
                      return -1;
                  }
              }
              int ret = zend_compare(o1, &casted);
              zval_ptr_dtor(&casted);
              return ret;
          }
          return ZEND_UNCOMPARABLE;
      }

关键的一点是 cast_object 到一个 int类型。但标准的cast只能到string，到int就返回FAILURE。