Issue I am coming across is that my calculation is not coming out correctly, it will display "0s" if nothing is entered, also it shows the previous entered data and then the newly entered info, but multiple times. It should only be showing the gravity multiplied by the weight entered.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Lab 03 - Planet Weight Calculator</title>


		<?php
			$planets = array( "Mercury","Venus","Earth","Mars","Jupiter","Saturn","Uranus","Neptune","Pluto" ); //array to set the dropdown

			$choice = "Mercury";

			if( isset( $_POST['choice'] ) ) {
				$choice = $_POST['choice'];
			}
		?>
        
        <?php
			$weight = "";
			
			if( ! empty( $_POST['weight'] ) ) {
				$weight = $_POST['weight'];
			}

		?>


</head>

<body>
		<?php
			$planet_file = fopen( "PLANET.TXT", "r" ); //will error if file is not found
			if( ! $planet_file ) {
				echo "No such file to perform task.</body></html>";
				exit;
			}

		?>


	<h1>Planet Weight Calculator</h1>
    
		<form action="lab03.php" method="post">
			<label for="choice">Choose a Planet</label><br/> 
			<select name="choice" id="choice">
				<?php
					foreach( $planets as $planet ) { //conditional to make sure that users choice of planet sticks
						if( $choice == $planet ) {
							echo "<option selected>$planet</option>";
						} else {
							echo "<option>$planet</option>";
						}
					}
					
				?>
                
               </select><br/>
               
               <label for="weight">Enter the weight of an item: </label><br/>
               <input type="text" name="weight" id="weight" value="<?php echo $weight ?>"/>

               

			<input type="submit" value="Submit"/>
		</form>
        
        

               <?php
			  		   
			   if( $choice == "Mercury" ) { //chooses the correct picture for the chosen planet
				   echo "<img src='PlanetImages/Planet1.jpg' />";  
				   } else if ( $choice == "Venus" ) {
					   echo "<img src='PlanetImages/Planet2.jpg' />";
					    } else if ( $choice == "Earth" ) {
					   echo "<img src='PlanetImages/Planet3.jpg' />";
					    } else if ( $choice == "Mars" ) {
					   echo "<img src='PlanetImages/Planet4.jpg' />";
					    } else if ( $choice == "Jupiter" ) {
					   echo "<img src='PlanetImages/Planet5.jpg' />";
					    } else if ( $choice == "Saturn" ) {
					   echo "<img src='PlanetImages/Planet6.jpg' />";
					    } else if ( $choice == "Uranus" ) {
					   echo "<img src='PlanetImages/Planet7.jpg' />";
					    } else if ( $choice == "Neptune" ) {
					   echo "<img src='PlanetImages/Planet8.jpg' />";
					    } else if ( $choice == "Pluto" ) {
					   echo "<img src='PlanetImages/Planet9.jpg' />";
				   }
				   
				?>
                


         <hr />
         
         
                 <?php
			   	if( $weight == "" )
				echo "<font color='red'>You must enter a weight!</font><br/>"; //fancy statements to let the user know
				?>
               
              	<?php
			   	if ( $choice == "Earth" ) {
				echo "<font color='red'>You must choose a planet other than Earth!</font><br/>";  //fancy statements to let the user know
				}
			   	?>
        
		<?php

			$planet =  "";
			$gravity = "";
			$field = "";
			
			
					
			$planet = array( );

			
			

			

				while(! feof($planet_file)) {
					$char = fgetc($planet_file);
					
					if($char == " "){
						$planet = $field;
						$field = "";
							} else if($char == "\n"){
								$gravity = $field;
								$field = "";
									} else {
									$field .= $char;
									}
									
									
								
									
								if( $choice == $planet ) {
									echo $gravity*$weight;
									} else if ( $choice == "Earth" ) {
									 echo $gravity = " ";
				}
								} //end while 
								

		

			fclose( $planet_file );
		?>
</body>
</html>

Hi,

try to set up an AND operator, like

if(($gravity == 0)&&($weight == 0)){
## show something, instead of the calculated value here.

}

else{

## show calculation if both the gravity and the weight are greater than zero

}

Test your codes by removing the value in

<input type="text" name="weight" id="weight" value="<?php echo $weight ?>"/>
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