PHP函数和if / else语句

I am trying to write a script that includes if/else statements and functions. some background

• $parts first character should have the letter "N"
• $desc is suppose to be at least one character long
• $price needs to be positive (0 or higher)

if all three of theses requirements are met then it should say "data accepted" if something is not met (one or all) the "Invalid...." needs to show.

can someone tell me what part of my script I should look at.

<?php
$parts = $_POST["parts"];
$desc  = $_POST["desc"];
$price = $_POST["price"];

$pa = substr($parts, 0, 1);
$de = strlen($desc);

if ($pa != "N")
 {echo "Invalid Part Number";}
else
 if ($de <= 1)
  {echo "Invalid Description Length";}
 else
  if ($price <= 0)
   {echo "Invalid Price";}
    else
     {echo "Data Accepted";}
?>

The second if should be if($de==1) $de=1 will always return true.

Also add semicolons after each statement.

$parts = $_POST["parts"];
$desc  = $_POST["desc"];
$price = $_POST["price"];

the second if should be if($de < 1) you can have if($de == 1) if its always going to be one character long but this will work if its 1 or more

Your requirement:-

$parts first character should have the letter "N"

$desc is suppose to be at least one character long

$price needs to be positive (0 or higher)

Solution:-

$parts = $_POST["parts"];
$desc  = $_POST["desc"];
$price = $_POST["price"];

$pa = substr($parts, 0, 1);
$de = strlen($desc);

if($pa != 'N') {
    echo "Invalid Part Number";
} elseif($de < 1) {
    echo "Invalid Description Length";
} elseif($price < 0) {
    echo "Invalid Price";
} else {
    echo "Data Accepted";
}

    <?php
    $parts = '';
    $desc = '';
    $price = 0;
    if ($_POST['parts'] != 'n')
    {
    echo 'Not equal to n<br>';
    }
    else {
    'Accepted input<br>';
    }
    $desc = strlen($_POST['desc']);
    if ($desc < 1)
    {
    echo 'Input less than 1<br>';
     }
    else {
    echo 'Accepted input<br>';
    }
    if ($_POST['price'] < 0)
    {
    echo 'Input below 0<br>';
    }
    else {
    echo 'Input accepted<br>';
    }
    ?>