is_int和模数％1之间的差异？

Question

I ran the following code, to test if a number was divisible by 7 and then return only if true.

is_int gives me what I think, but using modulus to check if it is an integer (%1) I get floats too.

for ($i = 100; $i < 222; $i++) {
        $dividedBy7 = $i/7;
        if(is_int($dividedBy7)){
            echo 'is int thinks '.$dividedBy7.'</br>';
        }
        if($dividedBy7 % 1 == 0){
            echo 'modulus thinks '.$dividedBy7.'</br>';
        }
}

OUTPUT

modulus thinks 14.2857142857, modulus thinks 14.4285714286 etc

is int thinks15, 16 etc

What is wrong with my understanding of modulus?

EDIT I appreciate that %7 is the correct use of modulus in this example, but this is a simplification of the situation.

Answer 1

Answering your question: modulus operator (so, %) is an integer operator. Thus, it expects operands to be integer. If not, it will convert them to integer. That stands from implementation:

ZEND_API int mod_function(zval *result, zval *op1, zval *op2 TSRMLS_DC) /* {{{ */
{
    zval op1_copy, op2_copy;
    long op1_lval;

    zendi_convert_to_long(op1, op1_copy, result);
    op1_lval = Z_LVAL_P(op1);
    zendi_convert_to_long(op2, op2_copy, result);

    if (Z_LVAL_P(op2) == 0) {
        zend_error(E_WARNING, "Division by zero");
        ZVAL_BOOL(result, 0);
        return FAILURE;         /* modulus by zero */
    }

    if (Z_LVAL_P(op2) == -1) {
        /* Prevent overflow error/crash if op1==LONG_MIN */
        ZVAL_LONG(result, 0);
        return SUCCESS;
    }

    ZVAL_LONG(result, op1_lval % Z_LVAL_P(op2));
    return SUCCESS;
}

So as you can see,

    zendi_convert_to_long(op1, op1_copy, result);
    op1_lval = Z_LVAL_P(op1);
    zendi_convert_to_long(op2, op2_copy, result);

will produce the conversion. That's why it's:

var_dump(14.4 % 7); //int(0) since (int)14.4 is 14 which is dividable by 7

Proper way would be to check the reminder from division by 7, thus,

if($i % 7 == 0)
{
   //$i is dividable by 7
}

Use integer operators with integer operands to avoid any unexpected behavior.