Creating a table that multiplies height by weight - php

Question

How would I create a table that multiples height by weight?
I have no idea how to figure it out!
I am trying to create a BMI calculator.
// collect values from a form sent with method=get
$min_weight = mysql_real_escape_string($_GET["min_weight"]);
$max_weight = mysql_real_escape_string($_GET["max_weight"]);
$min_height = mysql_real_escape_string($_GET["min_height"]);
$max_height = mysql_real_escape_string($_GET["max_height"]);
?>
<table>
<tr>
<td>Key:</td>
<td class="good show">Healthy (20-25)</td>
<td cla ss="warning show">Overweight (25-30)</td>
<td class="bad show">Unhealthy ( -20 or 30+)</td>
</tr>
</table>
<table border="1">
<?php
echo "<tr><td>Height →<br>Weight ↓</td>";
for ( $i = $min_height; $i <= $max_height; $i+=5 )
{
echo "<td>{$i}</td>";
}
echo "</tr>";
for ( $j = $min_weight; $j <= $max_weight; $j+=5 )
{
echo "<tr>";
echo "<td>{$j}</td>";
echo "</tr>";
}

Answer 1

This should do the job, i've also put some isset()'s:
<?php
// collect values from a form sent with method=get
$min_weight = isset($_GET["min_weight"]) ? mysql_real_escape_string($_GET["min_weight"]):0;
$max_weight = isset($_GET["max_weight"]) ? mysql_real_escape_string($_GET["max_weight"]):0;
$min_height = isset($_GET["min_height"]) ? mysql_real_escape_string($_GET["min_height"]):0;
$max_height = isset($_GET["max_height"]) ? mysql_real_escape_string($_GET["max_height"]):0;
?>
<table>
<tr>
<td>Key:</td>
<td class="good show">Healthy (20-25)</td>
<td class="warning show">Overweight (25-30)</td>
<td class="bad show">Unhealthy ( -20 or 30+)</td>
</tr>
</table>
<?php
$table = '<table border="1">';
$table .= '<tr><td>Height →<br>Weight ↓</td>';
for ($i = $min_height;$i <= $max_height;$i += 5){
$table .= "<td>$i</td>";
}
$table .= "</tr>";
for($j = $min_weight; $j <= $max_weight;$j += 5){
$table .= "<tr><td>$j</td>";
for ($i = $min_height;$i <= $max_height;$i += 5){
$table .= '<td>'. $i * $j .'</td>';
}
$table .= '</tr>';
}
$table .= '</table>';
echo $table;
?>

Answer 2

Even though this works is it wrong to have the table border outside of the php tags?
<table>
<tr>
<td>Key:</td>
<td class="good show">Healthy (20-25)</td>
<td class="warning show">Overweight (25-30)</td>
<td class="bad show">Unhealthy ( -20 or 30+)</td>
</tr>
</table>
<table border="1">
<?php
echo "<tr><td>Height →<br>Weight ↓</td>";
for ( $j = $min_height; $j <= $max_height; $j+=5 )
{
echo "<td>{$j}</td>";
}
for ( $i = $min_weight; $i <= $max_weight; $i+=5 )
{
echo "<tr><td>{$i}</td>";
for ( $j = $min_height; $j <= $max_height; $j+=5 )
{
$var = number_format(($i)/(($j/100)*($j/100)),'2','.','');
{
echo "<td class='warning'>";
}
echo $var;
echo "</td>";
}
echo "</tr>";
}
?>
</table>