Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Cell/Coordinate.php
public static function columnIndexFromString($pString)
    {
        //    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 = [];

        if (isset($indexCache[$pString])) {
            return $indexCache[$pString];
        }
        //    It's surprising how costly the strtoupper() and ord() calls actually are, so we use a lookup array rather than use ord()
        //        and make it case insensitive to get rid of the strtoupper() as well. Because it's a static, there's no significant
        //        memory overhead either
        static $columnLookup = [
            'A' => 1, 'B' => 2, 'C' => 3, 'D' => 4, 'E' => 5, 'F' => 6, 'G' => 7, 'H' => 8, 'I' => 9, 'J' => 10, 'K' => 11, 'L' => 12, 'M' => 13,
            'N' => 14, 'O' => 15, 'P' => 16, 'Q' => 17, 'R' => 18, 'S' => 19, 'T' => 20, 'U' => 21, 'V' => 22, 'W' => 23, 'X' => 24, 'Y' => 25, 'Z' => 26,
            'a' => 1, 'b' => 2, 'c' => 3, 'd' => 4, 'e' => 5, 'f' => 6, 'g' => 7, 'h' => 8, 'i' => 9, 'j' => 10, 'k' => 11, 'l' => 12, 'm' => 13,
            'n' => 14, 'o' => 15, 'p' => 16, 'q' => 17, 'r' => 18, 's' => 19, 't' => 20, 'u' => 21, 'v' => 22, 'w' => 23, 'x' => 24, 'y' => 25, 'z' => 26,
        ];

        //    We also use the language construct isset() rather than the more costly strlen() function to match the length of $pString
        //        for improved performance
        if (isset($pString[0])) {
            if (!isset($pString[1])) {
                $indexCache[$pString] = $columnLookup[$pString];

                return $indexCache[$pString];
            } elseif (!isset($pString[2])) {
                $indexCache[$pString] = $columnLookup[$pString[0]] * 26 + $columnLookup[$pString[1]];

                return $indexCache[$pString];
            } elseif (!isset($pString[3])) {
                $indexCache[$pString] = $columnLookup[$pString[0]] * 676 + $columnLookup[$pString[1]] * 26 + $columnLookup[$pString[2]];

                return $indexCache[$pString];
            }
        }

        throw new Exception('Column string index can not be ' . ((isset($pString[0])) ? 'longer than 3 characters' : 'empty'));
    }
public static function columnIndexFromString($pString)
    {
        //    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 = [];

        if (isset($indexCache[$pString])) {
            return $indexCache[$pString];
        }
        //    It's surprising how costly the strtoupper() and ord() calls actually are, so we use a lookup array rather than use ord()
        //        and make it case insensitive to get rid of the strtoupper() as well. Because it's a static, there's no significant
        //        memory overhead either
        static $columnLookup = [
            'A' => 1, 'B' => 2, 'C' => 3, 'D' => 4, 'E' => 5, 'F' => 6, 'G' => 7, 'H' => 8, 'I' => 9, 'J' => 10, 'K' => 11, 'L' => 12, 'M' => 13,
            'N' => 14, 'O' => 15, 'P' => 16, 'Q' => 17, 'R' => 18, 'S' => 19, 'T' => 20, 'U' => 21, 'V' => 22, 'W' => 23, 'X' => 24, 'Y' => 25, 'Z' => 26,
            'a' => 1, 'b' => 2, 'c' => 3, 'd' => 4, 'e' => 5, 'f' => 6, 'g' => 7, 'h' => 8, 'i' => 9, 'j' => 10, 'k' => 11, 'l' => 12, 'm' => 13,
            'n' => 14, 'o' => 15, 'p' => 16, 'q' => 17, 'r' => 18, 's' => 19, 't' => 20, 'u' => 21, 'v' => 22, 'w' => 23, 'x' => 24, 'y' => 25, 'z' => 26,
        ];

        //    We also use the language construct isset() rather than the more costly strlen() function to match the length of $pString
        //        for improved performance
        if (isset($pString[0])) {
            if (!isset($pString[1])) {
                $indexCache[$pString] = $columnLookup[$pString];

                return $indexCache[$pString];
            } elseif (!isset($pString[2])) {
                $indexCache[$pString] = $columnLookup[$pString[0]] * 26 + $columnLookup[$pString[1]];

                return $indexCache[$pString];
            } elseif (!isset($pString[3])) {
                $indexCache[$pString] = $columnLookup[$pString[0]] * 676 + $columnLookup[$pString[1]] * 26 + $columnLookup[$pString[2]];

                return $indexCache[$pString];
            }
        }

        throw new Exception('Column string index can not be ' . ((isset($pString[0])) ? 'longer than 3 characters' : 'empty'));
    }
Column index from string.

@param string $pString eg 'A'

@return int Column index (A = 1)