How to select and use multiple formulae in the drop-down of form in PHP
In this tutorial, we will practice the code of using/selecting multiple formulae in the drop down of form as shown below in the figure.
<?php
$result=0;
$head=0;
$velocity=0;
$coefficient=0;
$gravity= 9.8;
if(isset($_POST["submit"]))
{
$head=$_POST["head"];
$coefficient=$_POST["coefficient"];
$velocity=$_POST["velocity"];
if($head==0)
{
$head=1;
}
if($coefficient==0)
{
$coefficient=1;
}
if($velocity==0)
{
$velocity=1;
}
$select_option=$_POST["select_option"];
if($select_option=="head_Loss")
{
$v=pow($velocity,2);
$x=$v/(2*$gravity);
$head=$coefficient*$x;
}
elseif($select_option=="velocity")
{
$x=2*$gravity*$head;
$result=$x/$coefficient;
$velocity=sqrt($result);
}
elseif ($select_option=="coefficient") {
$x=(2*$gravity)/pow($velocity,2);
$coefficient=$head*$x;
}
}
unset($_POST["submit"]);
?>
<html>
<head>
<title>Minor Losses Calculator</title>
<style>
body{
background-color:white;
height: 100%;
background-image: linear-gradient(to bottom,#006600,#006600 1%, white 40%);
}
h1{
color: white;
text-align:center;}
</style>
</head>
<body>
<br>
<br>
<br>
<br>
<br>
<h1>Minor Losses Calculation</h1>
<form method="POST" action="#">
<table cellpadding="2" cellpadding="2" align ='center' style="border:double #333333; vertical-align:bottom"; >
<tr>
<td><b>I want to calculate </b></td>
<td><select name="select_option" id="select_option" onChange="val()">
<option value="head_Loss">Head Loss (HL)</option>
<option value="velocity">Velocity (v)</option>
<option value="coefficient">Closed Conduits Energy Loss Coefficient(K)</option>
</select></td>
</tr>
<tr>
<td><b>Velocity = </b></td>
<td><input type="text" id="velocity" name="velocity" value="<?php echo $velocity ?>" ><b>m/s</b></td>
</tr>
<tr>
<td><b>Closed Conduits Energy Loss Coefficient(K) = </b></td>
<td><input type="text" id="coefficient" value="<?php echo $coefficient?>" name="coefficient"></td>
</tr>
<tr>
<td><b>Head Loss(H<sub>L</sub>) = </b> </td>
<td><input type="text" readonly="yes" id="head" value="<?php echo $head?>" name="head"><b>m</b></td>
</tr>
<tr>
<td>
</td>
</tr>
<tr>
<td><input type="button" onclick="resetval()" value="Reset" name="reset" value="Reset" style="font-size:12pt; text-align: center; color:white; cursor: pointer; background-color:black ;border:#336600;padding:5px 20px;><font color='"white"'></font></td>
<td><input type="submit" name="submit" style="font-size:16px; text-align: center; color:white; cursor: pointer; background-color:#006600; border:black; padding:5px 80px; > <font color: '"white" '></font></td>
</tr>
</table>
</form>
<script type="text/javascript">
function val() {
d = document.getElementById("select_option").value;
if(d=="head_Loss")
{
document.getElementById("head").readOnly=true;
document.getElementById("velocity").readOnly=false;
document.getElementById("coefficient").readOnly=false;
}
else if(d=="velocity")
{
document.getElementById("head").readOnly=false;
document.getElementById("velocity").readOnly=true;
document.getElementById("coefficient").readOnly=false;
}
else if (d=="coefficient")
{
document.getElementById("head").readOnly=false;
document.getElementById("velocity").readOnly=false;
document.getElementById("coefficient").readOnly=true;
}
}
function resetval()
{
document.getElementById("head").value=null;
document.getElementById("velocity").value=null;
document.getElementById("coefficient").value=null;
}
</script>
<p><h3> </h3>
</body>
</html>