Generic PHP function to get data from MySQL database - php

Question

I'm creating a web application that relies heavily upon getting data from MySQL using PHP. In ~50 functions I have very similar code requesting single data values from MySQL:
function get_profile_picture($whatmember) {
global $connection;
$whatmember = mysql_prep($whatmember);
$query = "SELECT picture_location FROM members WHERE member_id={$whatmember} LIMIT 1";
$returnval = mysqli_query($connection,$query);
if(!$returnval) {
return "Query failed: " . mysqli_error($connection);
}
if(mysqli_num_rows($returnval) > 0 ) {
$row = mysqli_fetch_assoc($returnval);
return $row["picture_location"];
}
return false;
}
So my question is this: is there a generic AND safe way to make the function so that I can just input "SELECT what-value FROM what-database.what-table WHERE what-criteria=what-value" that allows for arrays of results as well as single values? I made an attempt with the following, but it obviously is a hack and slash method that only gets single values:
function get_single_value($database_name,$column_name,$table_name,$criteria,$criteria_value) {
$database_name = mysql_prep($database_name);
$column_name = mysql_prep($column_name);
$table_name = mysql_prep($table_name);
$criteria = mysql_prep($criteria);
$criteria_value = mysql_prep($criteria_value);
if(!empty($column_name) && !empty($table_name) && !empty($criteria) && !empty($database_name)) {
global $connection;
global $gamesconnection;
global $locationconnection;
if($database_name=="connection") {
$database_connection = $connection;
} else if ($database_name=="games") {
$database_connection = $gamesconnection;
} else if ($database_name=="locations") {
$database_connection = $locationconnection;
} else {
die("Database connection doesn't exist for {$database_name}.");
}
$query = "SELECT {$column_name} FROM {$table_name} WHERE {$criteria}='{$criteria_value}' LIMIT 1";
$result = mysqli_query($database_connection,$query);
if(!$result) {
die("Unable to get {$column_name} from {$table_name}. Error: " . mysqli_error($database_connection) . " Query: " . $query);
}
if(mysqli_num_rows($result)>0) {
$row = mysqli_fetch_assoc($result);
return $row[$column_name];
}
}
return false;
}
And my get_profile_picture() function would then look more like this:
function get_profile_picture($whatmember) {
return get_single_value("connection","picture_location","members","member_id",$whatmember);
}
I'm still pretty new to PHP and MySQL so any pointers to improve my code would be great as well. Thanks in advance!

Answer 1

Alright I wrote my own. It might not have all the security of PDO, but I don't have the learn another framework in order to use it.
function get_from_database($database_variable) {
//PASS IN $database_variable WHICH IS AN OBJECT CONTAINING THE FOLLOWING POSSIBLE VALUES
$database_name = $database_variable["database_name"]; //DATABASE NAME
$column_name = $database_variable["column_name"]; //COLUMN(S) BEING REQUESTED
$table_name = $database_variable["table_name"]; //TABLE BEING SEARCHED
$criteria = $database_variable["criteria"]; // 'WHERE X'
$limit = $database_variable["limit"]; //ANY LIMITS, IF REQUIRED
$group_by = $database_variable["group_by"]; //ANY GROUPING, IF REQUIRED
$order_by = $database_variable["order_by"]; //ANY SORT ORDERING, IF REQUIRED
if(!empty($column_name) && !empty($table_name)&& !empty($database_name)) {
global $connection;
global $gamesconnection;
global $locationconnection;
global $olddataconnection;
if($database_name=="connection") {
$database_connection = $connection;
} else if ($database_name=="games") {
$database_connection = $gamesconnection;
} else if ($database_name=="locations") {
$database_connection = $locationconnection;
} else if ($database_name=="olddata") {
$database_connection = $olddataconnection;
} else {
error_log("\nDatabase connection doesn't exist for {$database_name}." . get_backtrace_info());
return false;
}
if(is_null($limit)) {
//IF LIMIT NOT SUPPLIED, MAKE LIMIT 0, IE NO LIMIT
$limit = 0;
}
if(is_int($limit)==false) {
//NOT AN INTEGER
error_log("\nError in limit provided: " . $limit . get_backtrace_info());
return false;
}
$query = " SELECT {$column_name}
FROM {$table_name} " . (!empty($criteria) /*CHECK IF CRITERIA WAS REQUIRED*/ ? "
WHERE {$criteria} " : "") . (!empty($group_by) /*CHECK IF GROUP BY WAS REQUIRED*/ ? "
GROUP BY {$group_by} " : "") . (!empty($order_by) /*CHECK IF ORDER BY WAS REQUIRED*/ ? "
ORDER BY {$order_by} " : "") . ($limit!==0 /*CHECK IF LIMIT WAS REQUIRED*/ ? "
LIMIT {$limit} " : "");
$result = mysqli_query($database_connection,$query);
if(!$result) {
error_log("\nUnable to process query, got error: " . mysqli_error($database_connection) . "\nQuery: " . $query . get_backtrace_info());
return false;
}
if(mysqli_num_rows($result)>0) {
//RESULT SUPPLIED
$row_array = array();
while($row = mysqli_fetch_assoc($result)) {
$row_array[] = $row;
}
mysqli_free_result($result);
return $row_array;
}
}
return false;
}
Function to trace function call back to source:
function get_backtrace_info(){
//GET INFORMATION ON WHICH FUNCTION CAUSED ERROR
$backtrace = debug_backtrace();
$backtrace_string = "";
for($i=0;$i<count($backtrace);$i++) {
$backtrace_string .= '\n';
if($i==0) {
$backtrace_string .= 'Called by ';
} else {
$backtrace_string .= 'Which was called by ';
}
$backtrace_string .= "{$backtrace[$i]['function']} on line {$backtrace[$i]['line']}";
}
return backtrace_string;
}
Now I can request data from MySQL as follows:
Single value requested:
function get_profile_picture($whatmember) {
$linked_member_code = get_linked_member_code($whatmember);
return get_from_database([ "database_name" => "connection",
"column_name" => "picture_location",
"table_name" => "members",
"criteria" => "linked_member_code='{$linked_member_code}' AND team_id=0",
"limit" => 1
])[0]["picture_location"];
}
2 values requested:
function get_city_and_region_by_id($whatid) {
$row = get_from_database([ "database_name" => "locations",
"column_name" => "city, region",
"table_name" => "cities",
"criteria" => "row_id={$whatid}",
"limit" => 1
]);
return $row[0]["city"] . ", " . $row[0]["region"];
}
Unknown number of rows:
function get_linked_teams($linkedmembercode) {
return get_from_database([ "database_name" => "connection",
"column_name" => "team_id",
"table_name" => "members",
"criteria" => "linked_member_code='{$linkedmembercode}' AND team_id!=0"
]);
}