php比较函数

最近浏览PHP语言的源码-比较函数

其实我说的比较函数不是字符串比较，而且当我用PHP 的数组排序时候需要比较函数

1，为什么用比较函数

   首先用比较函数的好处就是代码的抽象，其实就是只有满足比较函数的规则你就可以，按照你自己方式排序,不是降序和升序这些简单的规则！满足规则{-1,0,1}-1：代表是小于，0代表等于，1代表大小

2.用比较函数

ZEND_API int compare_function(zval *result, zval *op1, zval *op2) /* {{{ */{        int ret;        int converted = 0;        zval op1_copy, op2_copy;        zval *op_free, tmp_free;        while (1) {                switch (TYPE_PAIR(Z_TYPE_P(op1), Z_TYPE_P(op2))) {                        case TYPE_PAIR(IS_LONG, IS_LONG):                                ZVAL_LONG(result, Z_LVAL_P(op1)>Z_LVAL_P(op2)?1:(Z_LVAL_P(op1)<Z_LVAL_P(op2)?-1:0));                                return SUCCESS;                        case TYPE_PAIR(IS_DOUBLE, IS_LONG):                                Z_DVAL_P(result) = Z_DVAL_P(op1) - (double)Z_LVAL_P(op2);                                ZVAL_LONG(result, ZEND_NORMALIZE_BOOL(Z_DVAL_P(result)));                                return SUCCESS;                        case TYPE_PAIR(IS_LONG, IS_DOUBLE):                                Z_DVAL_P(result) = (double)Z_LVAL_P(op1) - Z_DVAL_P(op2);                                ZVAL_LONG(result, ZEND_NORMALIZE_BOOL(Z_DVAL_P(result)));                                return SUCCESS;                           case TYPE_PAIR(IS_DOUBLE, IS_DOUBLE):                                if (Z_DVAL_P(op1) == Z_DVAL_P(op2)) {                                        ZVAL_LONG(result, 0);                                } else {                                        Z_DVAL_P(result) = Z_DVAL_P(op1) - Z_DVAL_P(op2);                                        ZVAL_LONG(result, ZEND_NORMALIZE_BOOL(Z_DVAL_P(result)));                                }                                return SUCCESS;                        case TYPE_PAIR(IS_ARRAY, IS_ARRAY):                                ZVAL_LONG(result, zend_compare_arrays(op1, op2));                                return SUCCESS;                        case TYPE_PAIR(IS_NULL, IS_NULL):                        case TYPE_PAIR(IS_NULL, IS_FALSE):                        case TYPE_PAIR(IS_FALSE, IS_NULL):                        case TYPE_PAIR(IS_FALSE, IS_FALSE):                        case TYPE_PAIR(IS_TRUE, IS_TRUE):                                ZVAL_LONG(result, 0);                                return SUCCESS;                        case TYPE_PAIR(IS_NULL, IS_TRUE):                                ZVAL_LONG(result, -1);                                return SUCCESS;                        case TYPE_PAIR(IS_TRUE, IS_NULL):                                ZVAL_LONG(result, 1);                                return SUCCESS;                        case TYPE_PAIR(IS_STRING, IS_STRING):                                if (Z_STR_P(op1) == Z_STR_P(op2)) {                                        ZVAL_LONG(result, 0);                                        return SUCCESS;                                }                                ZVAL_LONG(result, zendi_smart_strcmp(op1, op2));                                return SUCCESS;                        case TYPE_PAIR(IS_NULL, IS_STRING):                                ZVAL_LONG(result, Z_STRLEN_P(op2) == 0 ? 0 : -1);                                return SUCCESS;                        case TYPE_PAIR(IS_NULL, IS_STRING):                                ZVAL_LONG(result, Z_STRLEN_P(op2) == 0 ? 0 : -1);                                return SUCCESS;                        case TYPE_PAIR(IS_STRING, IS_NULL):                                ZVAL_LONG(result, Z_STRLEN_P(op1) == 0 ? 0 : 1);                                return SUCCESS;                        case TYPE_PAIR(IS_OBJECT, IS_NULL):                                ZVAL_LONG(result, 1);                                return SUCCESS;                        case TYPE_PAIR(IS_NULL, IS_OBJECT):                                ZVAL_LONG(result, -1);                                return SUCCESS;                        default:                                if (Z_ISREF_P(op1)) {                                        op1 = Z_REFVAL_P(op1);                                        continue;                                } else if (Z_ISREF_P(op2)) {                                        op2 = Z_REFVAL_P(op2);                                        continue;                                }                                if (Z_TYPE_P(op1) == IS_OBJECT && Z_OBJ_HANDLER_P(op1, compare)) {                                        return Z_OBJ_HANDLER_P(op1, compare)(result, op1, op2);                                } else if (Z_TYPE_P(op2) == IS_OBJECT && Z_OBJ_HANDLER_P(op2, compare)) {                                        return Z_OBJ_HANDLER_P(op2, compare)(result, op1, op2);                                }                                if (Z_TYPE_P(op1) == IS_OBJECT && Z_TYPE_P(op2) == IS_OBJECT) {                                        if (Z_OBJ_P(op1) == Z_OBJ_P(op2)) {                                                /* object handles are identical, apparently this is the same object */                                                ZVAL_LONG(result, 0);                                                return SUCCESS;                                        }                                        if (Z_OBJ_HANDLER_P(op1, compare_objects) == Z_OBJ_HANDLER_P(op2, compare_objects)) {                                                ZVAL_LONG(result, Z_OBJ_HANDLER_P(op1, compare_objects)(op1, op2));                                                return SUCCESS;                                        }                                }                                if (Z_TYPE_P(op1) == IS_OBJECT) {                                        if (Z_OBJ_HT_P(op1)->get) {                                                zval rv;                                                op_free = Z_OBJ_HT_P(op1)->get(op1, &rv);                                                ret = compare_function(result, op_free, op2);                                                zend_free_obj_get_result(op_free);                                                return ret;                                        } else if (Z_TYPE_P(op2) != IS_OBJECT && Z_OBJ_HT_P(op1)->cast_object) {                                                ZVAL_UNDEF(&tmp_free);                                                if (Z_OBJ_HT_P(op1)->cast_object(op1, &tmp_free, ((Z_TYPE_P(op2) == IS_FALSE || Z_TYPE_P(op2) == IS_TRUE) ? _IS_BOOL : Z_TYPE_P(op2))) == FAILURE) {                                                        ZVAL_LONG(result, 1);                                                        zend_free_obj_get_result(&tmp_free);                                                        return SUCCESS;                                                }                                                ret = compare_function(result, &tmp_free, op2);                                                zend_free_obj_get_result(&tmp_free);                                                return ret;                                        }                                }                                if (Z_TYPE_P(op2) == IS_OBJECT) {                                        if (Z_OBJ_HT_P(op2)->get) {                                                zval rv;                                                op_free = Z_OBJ_HT_P(op2)->get(op2, &rv);                                                ret = compare_function(result, op1, op_free);                                                zend_free_obj_get_result(op_free);                                                return ret;                                        } else if (Z_TYPE_P(op1) != IS_OBJECT && Z_OBJ_HT_P(op2)->cast_object) {                                                ZVAL_UNDEF(&tmp_free);                                                if (Z_OBJ_HT_P(op2)->cast_object(op2, &tmp_free, ((Z_TYPE_P(op1) == IS_FALSE || Z_TYPE_P(op1) == IS_TRUE) ? _IS_BOOL : Z_TYPE_P(op1))) == FAILURE) {                                                        ZVAL_LONG(result, -1);                                                        zend_free_obj_get_result(&tmp_free);                                                        return SUCCESS;                                                }                                                ret = compare_function(result, op1, &tmp_free);                                                zend_free_obj_get_result(&tmp_free);                                                return ret;                                        } else if (Z_TYPE_P(op1) == IS_OBJECT) {                                                ZVAL_LONG(result, 1);                                                return SUCCESS;                                        }                                }                                if (!converted) {                                        if (Z_TYPE_P(op1) == IS_NULL || Z_TYPE_P(op1) == IS_FALSE) {                                                ZVAL_LONG(result, zval_is_true(op2) ? -1 : 0);                                                return SUCCESS;                                        } else if (Z_TYPE_P(op2) == IS_NULL || Z_TYPE_P(op2) == IS_FALSE) {                                                ZVAL_LONG(result, zval_is_true(op1) ? 1 : 0);                                                return SUCCESS;                                        } else if (Z_TYPE_P(op1) == IS_TRUE) {                                                ZVAL_LONG(result, zval_is_true(op2) ? 0 : 1);                                                return SUCCESS;                                        } else if (Z_TYPE_P(op2) == IS_TRUE) {                                                ZVAL_LONG(result, zval_is_true(op1) ? 0 : -1);                                                return SUCCESS;                                        } else {                                                zendi_convert_scalar_to_number(op1, op1_copy, result);                                                zendi_convert_scalar_to_number(op2, op2_copy, result);                                                converted = 1;                                        }                                         } else if (Z_TYPE_P(op1)==IS_ARRAY) {                                        ZVAL_LONG(result, 1);                                        return SUCCESS;                                } else if (Z_TYPE_P(op2)==IS_ARRAY) {                                        ZVAL_LONG(result, -1);                                        return SUCCESS;                                } else if (Z_TYPE_P(op1)==IS_OBJECT) {                                        ZVAL_LONG(result, 1);                                        return SUCCESS;                                } else if (Z_TYPE_P(op2)==IS_OBJECT) {                                        ZVAL_LONG(result, -1);                                        return SUCCESS;                                } else {                                        ZVAL_LONG(result, 0);                                        return FAILURE;                                }                }        }}

3.总结

       其实一般人认为比较函数很简单：就返回-1,0,1比较可以吗，为什么写的那么长。首选，php是弱类型语言，我们不能确定我们要比较两个数 是什么类型，比如数字，数字又分整型，浮点型，长整型，字符串,空等于是就注定长PHP的2个PHP的类型的个数= 2^(PHP类型的个数)

这就是一门语言，受欢迎的语言，考虑的方面比较多，全面性，

一门语言存在时间越长越长，它的补丁就越多，这个是在实践中检验出来的！你问它为什么，有可能它也不知道，反正就这样这个问题可以避免，有可能为了环境，你肯定见过#if HAVE_STRCOLL #endif 等等，也有可能避免它用函数的bug,也有可能每次对代码的抽象的不同，反正就源码就是一个难懂，难懂后面你可以看到一门语言的背后的故事，其实底层和我们做应用层原理一样，就是通过已有创造出我们想要东西，比如应用层：我们可以用php语言写一个web页面，底层只不过用c语言写一个tcp/ip 的写协议，