Show only the last result from mysql row - php

Question

I have a table
id | field1 | field2 | ... | field[x-1] | field[x]
1 | val1 | val2 | ... | val[x-1] | val[x]
And I'm doing this search
for($i = 1; $i <= $x; $i++){
$getvalue = mysql_query("SELECT * FROM table WHERE id='1' AND field".$i." LIKE 'some_value%'")or die(mysql_error());
while($row = mysql_fetch_array($getvalue)){
$j=$i+1;
$val = $row['field'.$j.''];
}
}
Some values in the table (val[1-x]) will be the same but I need to get only the LAST value. Limit 1 doesn't seem to work.
Update.
Unfortunately as David suggested, I can't change the database. It has to be as it is. I have a text file (a settings dump from a sensor) that I insert it line by line into the db and do a check to see if there are any errors. Most check run ok but I have a few lines in that I need to choose only the last one to do the check.
I have about 10 lines like this
D?
String
R?
String
...
D?
String
R?
String
I'm interested in the last string after R?. I use explode () and each value checked that they are with in limits.

Answer 1

Using ORDER BY id DESC LIMIT 1:
To get last row (with highest=last=newest id), you should use this:
SELECT * FROM table ORDER BY id DESC LIMIT 1;
Your updated code (with mysqli_ extension) to get last row:
$query= mysqli_query("SELECT * FROM table ORDER BY id DESC LIMIT 1") or die (mysqli_error());
}
$lastRow = mysqli_fetch_row($query);
echo $lastRow['id']; //get the last id
Using MAX():
You also can do it using SQL MAX() function:
SELECT * FROM table WHERE id=(SELECT MAX(id) FROM table)

Answer 2

Managed to get it working as I need it by doing this:
for($i = 1; $i <= 250; $i++){
$getvalue = mysql_query("SELECT * FROM full_dump WHERE file_name='".$_FILES['datafile']['name']."' AND field_".$i." LIKE ' 100,%'")or die(mysql_error());
while($row = mysql_fetch_array($getvalue)){
$i_temp = $i;
}
}
if($i_temp != NULL){
$getvalue = mysql_query("SELECT * FROM full_dump WHERE file_name='".$_FILES['datafile']['name']."' AND field_".$i_temp." LIKE ' 100,%'")or die(mysql_error());
while($row = mysql_fetch_array($getvalue)){
$r = $row['field_'.$i_temp.''];
}
}