How to create a custom function properly in PHP?

Question

I have created a custom function and I am getting this error. I dont think there is a "parse error" in my script.

Parse error: syntax error, unexpected ',', expecting '&' or T_VARIABLE in C:\wamp\www\web template\test.php on line 8

---

<?php
require('global script/php/dbConnect.php');
$varName = 'sd';
echo checkDBDuplicate('account_list', 'memberID', $varName);
function checkDBDuplicate(tableName, dbFieldName, variableName) 
{
 $tableName = tableName;
 $dbFieldName = dbFieldName;
 $variableName = variableName;
 $searchDuplicate = mysql_query('
 SELECT $dbFieldName
 FROM $tableName
 WHERE $dbFieldName = $variableName
 ') or die(mysql_error());
 $countRow = mysql_num_rows($searchDuplicate);
 return $countRow;
}
?>

The purpose of this script is to test if I can use a variable in a SELECT statement.

• Rene Pot: what is on line 8 of test.php
• JimmyBanks: in your sql statement make sure to escape the strings using mysql_real_escape_string

Answer 1

Variables should have a $ prefix. so

function checkDBDuplicate(tableName, dbFieldName, variableName) {

is wrong, make it

function checkDBDuplicate($tableName, $dbFieldName, $variableName) {

obviously, further on the same is true, so:

$tableName = tableName;
$dbFieldName = dbFieldName;
$variableName = variableName;

needs the same treatment

• JohnSmith: Ah thank you. It's working now. I thought I wasn't doing anything wrong because Javascript didn't need "var" in the function parameters.
• Nanne: Check. Just a remark: 'var' doesn't mean "i'm making a variable here"! It is never actually needed to declare a variable, it means "this variable should be global". Therefore it's logical it shouldn't go in a function. You could compare it with the php keyword "global", which also never goes into a function declaration. The $ means "a variable starts here" in php. There is no equivalent in Javascript, but certainly not the var keyword :)

Answer 2

function checkDBDuplicate(tableName, dbFieldName, variableName) {

Should be

function checkDBDuplicate($tableName, $dbFieldName, $variableName) {

and iside the function body:

$tableName = $tableName;
$dbFieldName = $dbFieldName;
$variableName = $variableName;

Answer 3

Your function should be like this:

<?php
require('global script/php/dbConnect.php');
$varName = 'sd';
echo checkDBDuplicate('account_list', 'memberID', $varName);
function checkDBDuplicate($tableName, $dbFieldName, $variableName) {
 $tableName = $tableName;
 $dbFieldName = $dbFieldName;
 $variableName = $variableName;
 $searchDuplicate = mysql_query("
 SELECT $dbFieldName
 FROM $tableName
 WHERE $dbFieldName = $variableName
 ") or die(mysql_error());
 $countRow = mysql_num_rows($searchDuplicate);
 return $countRow;
}
?>

Answer 4

The variables do not need to be assigned again !!!

Also some ' and ` are missing the the SQL query.

<?php
require('global script/php/dbConnect.php');
$varName = 'sd';
echo checkDBDuplicate('account_list', 'memberID', $varName);
function checkDBDuplicate($tableName, $dbFieldName, $variableName) {
 $searchDuplicate = mysql_query("
 SELECT `$dbFieldName`
 FROM `$tableName`
 WHERE `$dbFieldName` = '$variableName'
 ") or die(mysql_error());
 $countRow = mysql_num_rows($searchDuplicate);
 return $countRow;
}
?>