PHP hangs when getting num rows

[joecooper]

I have this same code elsewhere and it runs without a problem

 

Basically, the script wants to put some data in the database, but if the row already exisits, it needs to ignore it. I am using mysql_num_rows for this.

$sql="SELECT * FROM grid WHERE `id` = $nextcell LIMIT 1";
$result=mysql_query($sql);
$numrows = mysql_num_rows($result);
if ($numrows=0){  //nothing here, input data
    //code to insert
}

It hangs on the 2nd line.

 

I added "die("$nextcell");" to check it is returning a number, and it does.

Edited October 23, 2013 by joecooper

[joecooper]

It also hangs when using:

$sql="SELECT * FROM grid WHERE `id` = '$nextcell' LIMIT 1";
$result=mysql_query($sql);
                                   
 if (mysql_fetch_array($result)){

}

[Ch0cu3r]

If the script stops on mysql_query() then there is a problem with the query. To see if there is an error use mysql_error() to get the error from mysql.

$sql="SELECT * FROM grid WHERE `id` = $nextcell LIMIT 1";
if($result=mysql_query($sql)) // check that query executed
{
   $numrows = mysql_num_rows();
   if ($numrows=0){  //nothing here, input data
       //code to insert
   }
}
// mysql_query returned false, probably due to error
else
{
   echo 'MySQL Error: ' . mysql_error(); // display error from msyql
}

Edited October 23, 2013 by Ch0cu3r

[joecooper]

I rewrote the query and now is working fine. Odd as this code used to work on a previous server.

 $result = mysql_query("SELECT * FROM grid WHERE id=$nextcell LIMIT 1");
								   
 if(mysql_fetch_array($result) == false){

}

Thanks for your help.

[Barand]

Also

 

if ($numrows=0)

 

should be

 

if ($numrows==0)

[vinny42]

Also note that you are using one "=" sign, so you are putting zero into $numrows, instead of checking if $numrows has zero in it.

 

if ($numrows=0){ //nothing here, input data

 

should be

 

if ($numrows==0){ //nothing here, input data

 

and to make prevent this bug in future; teach yourself to always put the constant first:

 

if (0==$numrows)

 

Then, if you forget an "=" sign you will get an error from PHP because you cannot change the value of the constant "0".