Looping a MySQL query

[NoFear]

Greetings,
Is there anything functionally wrong with this code? There must be, 'cuz I keep getting errors:

for($i=0; $i<$numberofrows; $i++){
    $updatequery = "update ".$queryrows[$i]." set value = 5";
    $updateresult = mysql_query($updatequery);

$valuequery = "select gangname, value from ".$queryrows[$i];
$valueresult = mysql_query($valuequery);
$valuerows = mysql_fetch_array($valueresult);

echo "<b>Number of rows returned after update: ".$valuerows."<br><br></b>";
echo "<b>Value of first result: ".$valuerows[0]."<br><br></b>";
echo "\$i= ".$i."<br><br>";
}

I want to run an updating mysql query from an array of tables.

When I run this code, it seems that the first loop goes ok, then I get this error message:

Notice: Undefined offset: 1 in C:\Program Files\Apache Group\Apache2\htdocs\Test Stuff\individualtabletest.php on line 23

Notice: Undefined offset: 1 in C:\Program Files\Apache Group\Apache2\htdocs\Test Stuff\individualtabletest.php on line 27

Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource in C:\Program Files\Apache Group\Apache2\htdocs\Test Stuff\individualtabletest.php on line 29
Number of rows returned after update:

Value of first result:

$i= 1

[the_Igel]

echo "<b>Number of rows returned after update: ".$valuerows."<br><br></b>";

echo "<b>Value of first result: ".$valuerows[0]."<br><br></b>";

In the first echo $valuerows converted to string, in second it is used as array again.
I believe that's not all.
Please mark which line is 23.
And print $numberofrows and $queryrows.

[NoFear]

Alright. This is the entire code, that and the few lines above it:

$query = "select username from user_info";
$result = mysql_query($query);
$queryrows = mysql_fetch_row($result);
$numberofrows = mysql_num_rows($result);
echo "<b>Number of rows from initial query: ".$numberofrows."<br><br></b>";
echo "<b>Value of first result: ".$queryrows[0]."<br><br><b>";

for($i=0; $i<$numberofrows;){
    $updatequery = "update ".$queryrows[$i]." set value = 5";
    $updateresult = mysql_query($updatequery);

$valuequery = "select gangname, value from ".$queryrows[$i];
$valueresult = mysql_query($valuequery);
$valuerows = mysql_fetch_array($valueresult);

echo "<b>Number of rows returned after update: ".$valuerows."<br><br></b>";
echo "<b>Value of first result: ".$valuerows[0]."<br><br></b>";
echo "\$i= ".$i."<br><br>";
$i++;
}

This is the first TWO loops (there is one more) of the query. The first one works fine, the second one goes haywire. Lines 23 and 27 are the lines for "$updatequery=" and "$valuequery="

Number of rows from initial query: 3

Value of first result: user1

Number of rows returned after update: Array

Value of first result: user1gang

$i= 0


Notice: Undefined offset: 1 in C:\Program Files\Apache Group\Apache2\htdocs\Test Stuff\individualtabletest.php on line 22

Notice: Undefined offset: 1 in C:\Program Files\Apache Group\Apache2\htdocs\Test Stuff\individualtabletest.php on line 25

Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource in C:\Program Files\Apache Group\Apache2\htdocs\Test Stuff\individualtabletest.php on line 27
Number of rows returned after update:

Value of first result:

$i= 1