How do I convert a string into a DateTime without overwriting it OR modify the string without having-CodePudding

So I'm trying to make the code echo the date for the last saturday of february of the chosen year, but the method I attempted using completely overwrote the value of the string. I need the string to keep its value but still modify it into telling me the last saturday of february.

Heres the code:

´´´ <?php

$valdatum = date ("y-m-d H:i T", 0);

if(isset($_POST["valdatum"])) {
    $valdatum=filter_input(INPUT_POST, 'valdatum', FILTER_SANITIZE_SPECIAL_CHARS);
}
?>
<!DOCTYPE html>
<html lang="sv">
    <head>
        <title>Tjejvasan</title>
        <meta charset="utf-8">
    </head>
    <body>
        <form method="POST">
            <input type="date" name="valdatum" value="<?= $valdatum;?>">
            <input type="submit" value="Skicka">
        </form>
    <?php
    echo $valdatum;
    echo "<br>";
    $valdatum = new DateTime;
    $valdatum->modify('last saturday of february');
    $valdatum2 = $valdatum->format('Y-m-d');
    echo $valdatum2;
    ?>
    </body>
</html>

´´´

CodePudding user response：

You seem to have tied yourself in a few knots. I think this is what you need, although your description is not 100% clear:

if(isset($_POST["valdatum"])) {
    //use the date value submitted from the form
    $valdatum = $_POST["valdatum"];
}
else
{
  //use today's date when nothing else was submitted
  $valdatum = date("y-m-d");
}
?>
<!DOCTYPE html>
<html lang="sv">
    <head>
        <title>Tjejvasan</title>
        <meta charset="utf-8">
    </head>
    <body>
        <form method="POST">
            <input type="date" name="valdatum" value="<?= $valdatum;?>">
            <input type="submit" value="Skicka">
        </form>
    <?php
    //change the date to the last saturday in February of the same year
    $febDate = new DateTime($valdatum);
    $febDate->modify('last saturday of february');
    echo $febDate->format('Y-m-d');
    echo "<br>";
    ?>
    </body>
</html>