php - purpose of url encode?

Question

According to W3 schools :

URL encoding converts characters into a format that can be transmitted over the Internet. URLs can only be sent over the Internet using the ASCII character-set. Since URLs often contain characters outside the ASCII set, the URL has to be converted into a valid ASCII format.

I have a url encode statement following an insert query :

$Query = "INSERT INTO $Table_1 VALUES ('0','".mysql_escape_string($forename)."','".mysql_escape_string($surname)."', '".mysql_escape_string($username)."', '".mysql_escape_string($password)."', '".mysql_escape_string($email)."')";

if(mysql_db_query ($DBName, $Query)) {
$message = " - You have successfully registered";
header("Location: register.php?message=".urlencode($message));
} else {
die("Query was: $Query. Error: ".mysql_error());
}

Why is it necessary? Because characters such as @ in an e-mail address are being sent in the header redirect?

Isn't w3schools explanation enough? (it's not entirely correct though) — zerkms
– zerkms, Commented Apr 7, 2014 at 22:31
it mentions ASCII for some reason, while only a narrow subset of ASCII characters is allowed there. Check my answer for a further explanation. — zerkms
– zerkms, Commented Apr 7, 2014 at 22:46

Community · Accepted Answer · 2021-10-07 05:59:28Z

3

As per RFC3986

URI           = scheme ":" hier-part [ "?" query ] [ "#" fragment ]
query         = *( pchar / "/" / "?" )
pchar         = unreserved / pct-encoded / sub-delims / ":" / "@"
unreserved    = ALPHA / DIGIT / "-" / "." / "_" / "~"
pct-encoded   = "%" HEXDIG HEXDIG

And RFC2234

HEXDIG        = DIGIT / "A" / "B" / "C" / "D" / "E" / "F"
ALPHA         = %x41-5A / %x61-7A   ; A-Z / a-z
DIGIT         = %x30-39             ; 0-9

So it's required by a standard.

PS: as you can see @ is a valid character to be used in a query as-is without additional encoding.

edited Oct 7, 2021 at 5:59

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answered Apr 7, 2014 at 22:35

zerkms

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