i don't understand while ($x=somefunction())

koen

Actually I think I have problems understanding the truth value of an assignment. The while keeps looping until the expression contained within it ($x=somefunction()) returns false.

So is the value of ($x=5) 5? And is it only false when somefunction returns nothing (or false)? And if ($x=5) has 5 as value, is 5 also TRUE (otherwise the while loop wouldn't run)?

_theworks

read this [man]while[/man]

koen

I've read it about 100 times. What I don't understand in my example is how the expression valuates as true or false.

thanks for the answer though.

_theworks

stab in the dark
well isnt it wheather the function has succeeded or not? likes if the function succeeds it returns true on failure false?

rincewind456

Anything returned other than 0 is true be that 1 or 1,000,000.

koen

So the expression $a = 5 has value 5 and thus true?

rincewind456

yep!

Zanjo

Doesnt while execute statements while the function is true:

while($number = 12)
{
Blah blah blah
}

or a different case:
while(12 > $number)
{
$number++
}

_theworks

yeh but depends on your use of while i guess..

bpat1434

Actually I think I have problems understanding the truth value of an assignment. The while keeps looping until the expression contained within it ($x=somefunction()) returns false.

So is the value of ($x=5) 5? And is it only false when somefunction returns nothing (or false)? And if ($x=5) has 5 as value, is 5 also TRUE (otherwise the while loop wouldn't run)?

A while loop will continue to evaluate the expression within the parenthesis for a statement of TRUE or FALSE. So, if you have a statement that says:

while($x < 100){ $x++; }

You'd be saying that while $x is negative, or between 0 and 99.999 (since in this case '0' is less than 100, and the equation would evaluate to true), then increment $x. Once $x is 100.000 or more, STOP the while loop.

So by saying something like:

while($row = mysql_fetch_array($result)){echo $row['item'];}

We are saying that "until the result of mysql_fetch_array() is 'FALSE', we want the array returned to the variable $row. If mysql_fetch_array() returns a FALSE value, then we'll stop the loop."

So, in your example:

So is the value of ($x=5) 5? And is it only false when somefunction returns nothing (or false)? And if ($x=5) has 5 as value, is 5 also TRUE (otherwise the while loop wouldn't run)?

First off, your syntax is incorrect. If you're wanting to compare the value against a number/string, then you need to use double equal signs (==) or triple for a strict comparison (===). You can read more on this in the PHP manual under "Comparison Operators". So, in your statement, you're setting the value of $x to 5. Since you're always setting it, it should always run in a continuous loop, unless you physically exit or break the loop.

If you were to compare the value of $x to 5, then if $x was anything but 5, it would not run. If $x was equal to 5, it would since 5 = 5.

Normally, while loops are done for ranges of numbers:

while( ($x<4) && ($x>6) ){ $x++; }

Or to do something while a function returns true (like mysql_fetch_array() or any function you write that returns anything but a FALSE value).

I hope I helped you out a bit if you didn't already understand, or get the kind of answer you wanted.

~Brett