PHP prevents SQL injection

/*
Sometimes there is more than one variable submitted in the form, maybe a dozen or dozens. So is it a little troublesome to copy/paste addslashes() again and again? Since the data obtained from the form or URL appears in the form of an array, such as $_POST, $_GET), then customize a function that can "sweep the army"
*/
function quotes($content)
{
 //If magic_quotes_gpc=Off, then start processing
if (!get_magic_quotes_gpc()) {
//Determine whether $content is an array
if (is_array($content)) {
//If $content is an array, then Process each of its elements
foreach ($content as $key=>$value) {
$content[$key] = addslashes($value);
}
} else {
//If $content is not an array , then it will only be processed once
addslashes($content);
}
} else {
//If magic_quotes_gpc=On, then it will not be processed
}
//Return $content
return $content;
}
?>

php, SQL