src/Utils/BlockString.php
public static function value($rawString)
    {
        // Expand a block string's raw value into independent lines.
        $lines = preg_split("/\\r\\n|[\\n\\r]/", $rawString);

        // Remove common indentation from all lines but first.
        $commonIndent = null;
        $linesLength  = count($lines);

        for ($i = 1; $i < $linesLength; $i++) {
            $line   = $lines[$i];
            $indent = self::leadingWhitespace($line);

            if ($indent >= mb_strlen($line) ||
                ($commonIndent !== null && $indent >= $commonIndent)
            ) {
                continue;
            }

            $commonIndent = $indent;
            if ($commonIndent === 0) {
                break;
            }
        }

        if ($commonIndent) {
            for ($i = 1; $i < $linesLength; $i++) {
                $line      = $lines[$i];
                $lines[$i] = mb_substr($line, $commonIndent);
            }
        }

        // Remove leading and trailing blank lines.
        while (count($lines) > 0 && trim($lines[0], " \t") === '') {
            array_shift($lines);
        }
        while (count($lines) > 0 && trim($lines[count($lines) - 1], " \t") === '') {
            array_pop($lines);
        }

        // Return a string of the lines joined with U+000A.
        return implode("\n", $lines);
    }
public static function value($rawString)
    {
        // Expand a block string's raw value into independent lines.
        $lines = preg_split("/\\r\\n|[\\n\\r]/", $rawString);

        // Remove common indentation from all lines but first.
        $commonIndent = null;
        $linesLength  = count($lines);

        for ($i = 1; $i < $linesLength; $i++) {
            $line   = $lines[$i];
            $indent = self::leadingWhitespace($line);

            if ($indent >= mb_strlen($line) ||
                ($commonIndent !== null && $indent >= $commonIndent)
            ) {
                continue;
            }

            $commonIndent = $indent;
            if ($commonIndent === 0) {
                break;
            }
        }

        if ($commonIndent) {
            for ($i = 1; $i < $linesLength; $i++) {
                $line      = $lines[$i];
                $lines[$i] = mb_substr($line, $commonIndent);
            }
        }

        // Remove leading and trailing blank lines.
        while (count($lines) > 0 && trim($lines[0], " \t") === '') {
            array_shift($lines);
        }
        while (count($lines) > 0 && trim($lines[count($lines) - 1], " \t") === '') {
            array_pop($lines);
        }

        // Return a string of the lines joined with U+000A.
        return implode("\n", $lines);
    }
Produces the value of a block string from its parsed raw value, similar to
Coffeescript's block string, Python's docstring trim or Ruby's strip_heredoc.

This implements the GraphQL spec's BlockStringValue() static algorithm.