Database query always returns TRUE - php

Question

Trying to find if row exists in database. This code always returns TRUE. I want to add the row if it doesn't exist.
See test code below.
// CHECK IF RECORD EXISTS
if (array_key_exists('test', $_GET)) {
if(coupleRowExists($_GET['male'], $_GET['female'])) {
echo 'EXISTS';
} else {
echo 'Does NOT exist';
}
}
// CHECK DB FOR THIS COUPLE
function coupleRowExists($male, $female) {
global $db;
$sp_couple_exists = "SELECT EXISTS(SELECT 1 FROM `couples`
WHERE male = ? AND female = ? )";
return ($db->prepare($sp_couple_exists)->execute([$male, $female]));
}

Answer 1

This code:
return ($db->prepare($sp_couple_exists)->execute([$male, $female]));
Will return true when the database query is executed successfully, not necessarily if there is a result or not. Which, if you wrote the query properly, will be all the time.
If you want to find out if it actually returned a row, then you'll want to check for an actual returned row.
I would modify this a bit so it returns that and is a bit cleaner:
function coupleRowExists($male, $female) {
global $db;
$sql = "SELECT EXISTS(SELECT 1 FROM couples WHERE male = ? AND female = ?)";
$db->prepare ($sql);
$db->execute ([$male, $female]);
if ($db->rowCount()) {
return true;
} else {
return false;
}
}

Answer 2

execute() will return only true or false. Here's a link for a reference.
https://www.php.net/manual/en/pdostatement.execute.php
Here's a modified function for the same.
function coupleRowExists($male, $female) {
global $db;
$sql = "SELECT EXISTS(SELECT 1 FROM couples WHERE male = ? AND female = ?)";
$db->prepare ($sql);
$result = $db->execute ([$male, $female]);
if ($result && $db->rowCount() > 0) {
return true;
} else {
return false;
}
}

Answer 3

I agree with user3783243 in that rowCount does not always work with SELECT (see PHP Manual->PDOStatement::rowCount(). They recommend use of COUNT as follows:
function coupleRowExists($m, $f) {
global $db;
$sp = "SELECT COUNT(*) FROM `couples` WHERE male = ? AND female = ?";
$stmt = $db->prepare($sp);
$stmt->execute([$m, $f]);
$count = $stmt->fetchColumn();
return $count;
}
This has proven reliable.