I need to convert an integer (number of columns) into a string according to excel column naming scheme, like so:
1 => A
2 => B
25 => Z
26 => AA
28 => AC
51 => BA
Do you know of a smart and painless way to do this within php, or should I go about writing my own custom function?
You can do it with a simple loop:
$number = 51;
$letter = 'A';
for ($i = 1; $i <= $number; ++$i) {
++$letter;
}
echo $letter;
though if you're doing this frequently with higher values, it'll be a bit slow
or look at the stringFromColumnIndex() method in PHPExcel's Cell object that is used for exactly this purpose
public static function stringFromColumnIndex($pColumnIndex = 0) {
// Using a lookup cache adds a slight memory overhead, but boosts speed
// caching using a static within the method is faster than a class static,
// though it's additional memory overhead
static $_indexCache = array();
if (!isset($_indexCache[$pColumnIndex])) {
// Determine column string
if ($pColumnIndex < 26) {
$_indexCache[$pColumnIndex] = chr(65 + $pColumnIndex);
} elseif ($pColumnIndex < 702) {
$_indexCache[$pColumnIndex] = chr(64 + ($pColumnIndex / 26)) .
chr(65 + $pColumnIndex % 26);
} else {
$_indexCache[$pColumnIndex] = chr(64 + (($pColumnIndex - 26) / 676)) .
chr(65 + ((($pColumnIndex - 26) % 676) / 26)) .
chr(65 + $pColumnIndex % 26);
}
}
return $_indexCache[$pColumnIndex];
}
Note that the PHPExcel method indexes from 0, so you might need to adjust it slightly to give A from 1, or decrement the numeric value that you pass
There is also a corresponding columnIndexFromString() method in the cell object that returns a numeric from a column address
It can also be done quite easily with pure PHP:
function getCellFromColnum($colNum) {
return ($colNum < 26 ? chr(65+$colNum) : chr(65+floor($colNum/26)-1) . chr(65+ ($colNum % 26)));
}
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