function to check if data is on the database - php

Question

I create a function to find all firstname and lastname in my database all I want if that data is already exist I just want to output, error message
my question is how to create a function to check if data is already exist?
this is my function to find all data of firstname and lastname.
function find_student_by_firstname($firstname){
global $con;
$safe_firstname = prep($firstname);
$sql = "SELECT * ";
$sql .= "FROM studeprofile ";
$sql .= "WHERE FirstName = '{$safe_firstname}' ";
$sql .= "LIMIT 1";
$student_set = mysqli_query($con, $sql);
confirm_query($student_set);
if($student = mysqli_fetch_assoc($student_set)){
return $student;
} else {
return null;
}
}
function find_student_by_lastname($lastname){
global $con;
$safe_lastname = prep($lastname);
$sql = "SELECT * ";
$sql .= "FROM studeprofile ";
$sql .= "WHERE LastName = '{$safe_lastname}' ";
$sql .= "LIMIT 1";
$student_set = mysqli_query($con, $sql);
confirm_query($student_set);
if($student = mysqli_fetch_assoc($student_set)){
return $student;
} else {
return null;
}
}
this is my current function to check if data is already exist.
function match_fistname_lastname($lastname, $firstname){
$student_firstname = find_student_by_firstname($lastname);
if($student_firstname){
find_student_by_lastname($lastname);
} else {
return false;
}
}

Answer 1

If you mean by "data is already exist" that a person is in the database that matches to firstname and lastname, you don't have to execute two queries.
Use the and in mysql like this:
function find_student($firstname, $lastname){
global $con;
$safe_firstname = prep($firstname);
$safe_lastname = prep($lastname);
$sql = "SELECT * ";
$sql .= "FROM studeprofile ";
$sql .= "WHERE FirstName = '{$safe_firstname}' and LastName = '{$safe_lastname}' ";
$sql .= "LIMIT 1";
$student_set = mysqli_query($con, $sql);
confirm_query($student_set);
if($student = mysqli_fetch_assoc($student_set)){
return $student;
} else {
return null;
}
}