Forms and Files

Question

I’m making a form where I basically access a file .txt in the CSV format containing certain articles and their prices (e.g., cheese,2.10).

The program presents the list in a table, and below appear two fields that ask for "Article" and "Quantity", now what is the best way to make the program look for the article in the file, and tell if it exists or not, if the product exists, show the total multiplication of the quantity with the value of the product, which is in the second column of the file .txt.

For example, Product: Cheese, Quantity: 10, present 10x the price of total cheese below.

PS: Forms with the "Article" and "Quantity" fields disappear after being filled in.

So far my code is like this:

<?php

$br="</br>";
$file=fopen("produtos.txt","r");

echo "<table border='1'><tr><th>Artigos</th><th>Preco</th>";
while(!feof($file)) {
$registo=fgetcsv($file);

    echo"<tr>";
    echo"<td>".$registo[0]."</td>";
    echo"<td>".$registo[1]."</td>";
    echo"</tr>";

}
echo "</table>";
fclose($file);
?>

<?php
if ($_POST) {
    echo "Produto: ".$_POST["produto"]."<br>";
    echo "Quantidade ".$_POST["quantidade"]."<br>";
}
else {
?>

<form action="eta15.php" method="post">
Produto <input type="text" name="produto"><br>
Quantidade <input type="text" name="quantidade"><br>
<input type="Submit" name="enviar" value="Enviar">
</form>

<?php 
}
?>

I leave two printscreens, I hope they help in my question of the result in which I am:

Search form:

Result form:

Answer 1

For this just make a search condition, if the product is equal to the searched then calculates the total of the price multiplied by the quantity:

//...
$produto = isset( $_POST["produto"]    ) ? $_POST["produto"]    : "";
$qtd     = isset( $_POST["quantidade"] ) ? $_POST["quantidade"] : ""; 
$total   = 0;
$precoUN = 0;

while(!feof($file)) 
{
    $registo=fgetcsv($file);

    if( $produto == $registo[0] )
    {
        $total   = $registo[1] * $qtd;
        $precoUN = $registo[1];
    }

    echo"<tr>";
    echo"<td>".$registo[0]."</td>";
    echo"<td>".$registo[1]."</td>";
    echo"</tr>";

}
//...
if ($_POST) 
{
    echo "Produto:    ". $produto ."<br>";
    echo "Quantidade: ". $qtd     ."<br>";
    echo "Total       ". $total   ."<br>";
    echo "Preço/UN    ". $precoUN ."<br>";

    if ( $total > 0 ) 
    {
        echo "<br> O Produto selecionado existe";
    }
    else 
    { 
        echo "O Produto nao existe";
    }
}
//...

Answer 2

I solved with If, anything question there!..