i have a question.. i have a form in which a user adds his name, blood type and his age of birth.
at my sql table the column age_of_birth is type Date.

when i add a valid date, the date enters the table normally eg. 1990-02-21
when i add an invlaid date eg. 2000-50-50, the date enters the table like this 0000-00-00

i want to perform a check at the time the users presses the submit button.
a way, that i thought, to check was to do this:


if ( $age_of_birth == "0000-00-00" )
		echo "Invalid date";
but then i thought that the date have not entered the table yet and its value is still 2000-50-50
so the date will always enter the talbe..

more specifically this is my code and it has to do about donating organs. so i made a database to add the organs and keep a track of what's available.


if (isset($_POST['type_mosx']) && isset($_POST['oa_mosx']) && isset($_POST['age_mosx']) 
&& isset($_SESSION['username']))

	if ( $age_mosx == "0000-00-00" )
		echo "<font style='color:red;font-size:18px;'> Δώσατε λάθος ηλικία. Κάντε την καταχώρηση ξανά εισάγωντας σωστά την ηλικία.</font>
		<br /><br />";

		$sql="INSERT into mosx VALUES (NULL, '$type_mosx', '$oa_mosx', '$age_mosx', '$user')";
		@ $result = mysql_query($sql);
		if ($result) { echo "<font style='color:green;font-size:20px;'>Η καταχώρηση έγινε επιτυχώς</font>";}
		else { echo "Σφάλμα, Δοκιμάστε ξανα.";}


<h2 align="center">Καταχώρηση Οργάνου</h2>
	<p style='font-size:18px;'>Συμπληρώστε τα κενά με λατινικούς χαρακτήρες.</p>	
<form method="post" action="">
<table align=center>
<tr><td>Τύπος Μοσχεύματος:</td><td><input required="required" type="text" name="type_mosx" maxlength="30" /></td> </tr>
<tr><td>Ομάδα Αίματος:</td><td><input required="required" type="text" name="oa_mosx" maxlength="4" /></td> </tr>
<tr><td>Ηληκία Μοσχεύματος:</td><td><input required="required" type="text" name="age_mosx" maxlength="10"/></td>  </tr>

<tr><td colspan="2" align="right"><input type="submit" name="register" value="Καταχώρηση" /></td></tr>
		<br />
		<a href='index.php'>Επιστροφή στην αρχική σελίδα</a><br />
		<a href='logout.php'>Αποσύνδεση</a>



any help will be highly appreciated.

thank you all in advance.

Best regards.