mysql_fetch_row()

[livethedead]

Alright, I have a question regarding mysql_fetch_row. The manual says:

Returns an numerical array of strings that corresponds to the fetched row, or FALSE if there are no more rows

.

 

However,

<?php
$array = mysql_query();
$data = mysql_fetch_row($array);
while ($data) {
dosomething
}  

Turns into an endless loop. I'm sure I'm missing something and I'm just looking for an explanation. Thanks.

[livethedead]

I named mysql_query wrong, but my question still applies. Don't get confused by that.

[Pikachu2000]

while( $data = mysql_fetch_row( . . . ) ) {
     // do something
}

[livethedead]

Ah, I see. I don't quite understand how there is a difference between the two though. I take that back, after looking at it I understand. Appreciate it.

[scootstah]

The difference is that when you call mysql_fetch_row() it advances an internal pointer to the next row. If there isn't another row, it returns false. So basically in the while statement as soon as you have advanced through all of the rows, the statement is false and thus the while loop fails.

[AyKay47]

Okay. I'll break this down a bit. Let's start with your code:

 

<?php
$array = mysql_query();
$data = mysql_fetch_row($array);
while ($data) {
dosomething
}  

 

now, by declaring $data = mysql_fetch_row($array) outside of the while loop, you are setting the value of $data to a numerical array of strings that correspond to the fetched row, and this value will be static since it is outside of the while loop. the while loop that you have checks for that value to be true, which it always will be since it is a valid array.

 

The reason why you specify:

 

while($data = mysql_fetch_row())

 

inside of the while loop is because the nature of mysql_fetch_row(). I will quote from the manual here:

 

Returns a numerical array that corresponds to the fetched row and moves the internal data pointer ahead.

 

this means that when mysql_fetch_row() is called, the internal pointer is moved forward to the next results set row. So:

 

while($data = mysql_fetch_row())

 

will check for mysql_fetch_row() to be true every iteration of the loop. Once it returns false (there are no more rows to return) the loop is stopped.