[SOLVED] in_array error in a while loop

[ProblemHelpPlease]

I have a script that adds markers to a map based on latitude and longitude. To prevent to markers appearing on top of each other I am searching my database of markers and moving the marker to the right slightly if a current marker exists. The problem is that the markers stop moving to the right after the 3rd run through a while loop. I have managed to trace the error in the code.

 

Below is an example of the part of the code that fails.

 

<?php

$z = -8.1;

$arr = array("-2.1", "-11.1", "0.1", "-3.1", "-4.1", "-5.1", "-6.1", "-7.1", "-8.1", "-0.1", "1.1", "3.1", "2.1", "0.1");

while(in_array($z, $arr))

{

$z = $z + 1;

}

echo "final number ".$z . "<br>";

?>

 

This code should output the final number as -1.1 but when I run it it returns -3.1

 

If I use the same code but remove the - and the decimal place from the script then it works perfectly.

 

Any ideas as to what is wrong ???

[kenrbnsn]

You are seeing a side effect of how numbers are stored internally. Decimal numbers can not be represented exactly as binary numbers, so the condition fails.

 

Change the loop to:

<?php
while(in_array(number_format($z,1), $arr)) {
$z++; 
}?>

 

Ken

[ProblemHelpPlease]

I thought it might be related to how many values could be stored.

 

The numbers that the main script is using very from -11.999999 to 3.999999(theyalways have 6 digits after the decimal place and need to maintain this format when output from the while loop), and I am tring to add 0.0005 to the value if it already exists in the array. Do I need to make a change to the "number_format($z,1)"

 

I haven't used number_format before so i'm still getting my head around how its working.

[kenrbnsn]

When you're unfamiliar with a function, the best place to turn is the manual: number_format().

 

The second argument to the number_format() function is the number of decimal places.

 

Ken

[ProblemHelpPlease]

Thanks for the help ken

 

I'd looked at the manual but was confused with the various options.

 

I've implemented your code changed the decimal place value to 6 and it works ok now.