PHP：for循环和if语句

Question

I am currently studying a beginning PHP programming class and I need some assistance with one assignment I'm trying to solve. The assignment is to create a form where the user can enter a positive integer. Then, use a “for” loop to display that amount of horizontal lines created by the "hr" tag [Hint: <hr size=1 width=50% color='black'>]. Finally, use an if statement to perform “modulus” calculation. When the counter in the “for” loop is an even number set the width of the horizontal line to 50%; otherwise, set the width of the horizontal line to 100%.

Here's the code I have come up with thus far:

<?php

if ($_POST) { // if the form is filled out
$integer = $_POST["pi"];

$i = $integer;

for ($i = 1; $i <= $integer; $i++) {
if ($i % 2) { // modulus operator
echo "<hr size=1 width=50% color='black'>";
} else {
echo "<hr size=1 width=100% color='red'>";
}

}
}
else { // otherwise display the form
?>
<form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post">
Enter a <i>Positive Integer</i>:
<input type="text" name="pi" size=5>
<input type="submit" value="Check"></form></p>
<?php
}
?>

I can't post an image yet, but the sample output should be a 50% black horizontal rule, followed by a 100% red horizontal rule, until the integer entered is reached. In between each hr seems to have some spacing.

Answer 1

This line:

$i = $integer;

...is redundant, as soon as you say for($i = ..., $i will be overwritten. In your case, so it should be. Take that line out to start with.

Second, I think the problem you're having is that your lines aren't showing as black or red. Reason is that color is a font attribute and you should look at this post to find out how to change your color: Changing the color of an hr element

I suggest using class='black' and class='red' in your PHP and setting classes up in your CSS.