Check for a multiple amount of information in a database - php

Question

For my registration system, when the user registers, I want to make sure that their username, email, etc. is not taken. I have the code to check to see if the username exists, and I can probably do the same with the other stuff.
How can I do this without rewriting the block multiple times?
tl;dr: How can I check for more things in a database in a compact way?
$userquery = "SELECT * FROM users WHERE username = '$username'";
if ($result = $mysqli->query($userquery)) {
if ($result->num_rows > 0) {
die ("Username Already Exists.");
}
}

Answer 1

Use an 'OR' condition in your where clause
$userquery = "SELECT * FROM users WHERE username = '$username' OR email= '$email'";
if ($result = $mysqli->query($userquery)) {
if ($result->num_rows > 0) {
die ("Username/Email Already Exists.");
}
}
EDIT
ok then,
function doesitexist($mysqli,$table,$field,$value) {
$userquery = "SELECT * FROM $table WHERE $field = '$value' LIMIT 1";
if ($result = $mysqli->query($userquery)) {
if ($result->num_rows > 0) {
return true;
} else {
return false;
}
} else {
return('Error running Query');
}
}
ANOTHER EDIT just for fun. This should take an array of fields and values to check in one call.
$check = doesitexist($mysqli,'users',array('username'=>'bob','email'=>'someone#example.com'));
function doesitexist($mysqli,$table,$tocheck = array()) {
if (count($tocheck)>0) {
$where = '';
foreach ($tocheck as $field=>$value) {
$where .= $field." = '".addslashes($value)."' OR ";
}
$where = trim($where," OR ");
$userquery = "SELECT * FROM $table WHERE $where LIMIT 1";
if ($result = $mysqli->query($userquery)) {
if ($result->num_rows > 0) {
return true;
} else {
return false;
}
} else {
return('Error running Query');
}
} else {
return("No Fields/Values to check");
}
}