src/Debug/ErrorLevel.php
public static function toConstantString($level = null, $phpVer = null, $explicitStrict = true)
    {
        $string = '';
        $level = $level === null
            ? \error_reporting()
            : $level;
        $allConstants = self::getConstants($phpVer); // includes E_ALL
        $levelConstants = self::filterConstantsByLevel($allConstants, $level); // excludes E_ALL
        $eAll = $allConstants['E_ALL'];
        unset($allConstants['E_ALL']);
        if (\count($levelConstants) > \count($allConstants) / 2) {
            $string = 'E_ALL';
            foreach ($allConstants as $constantName => $value) {
                $isExplicit = $explicitStrict
                    && $constantName == 'E_STRICT';
                if (self::inBitmask($value, $level)) {
                    if (!self::inBitmask($value, $eAll) || $isExplicit) {
                        // only thing that wouldn't be in E_ALL is E_STRICT
                        $string .= ' | ' . $constantName;
                    }
                } else {
                    if (self::inBitmask($value, $eAll) || $isExplicit) {
                        $string .= ' & ~' . $constantName;
                    }
                }
            }
        } else {
            $string = \implode(' | ', \array_keys($levelConstants));
        }
        return $string ?: '0';
    }
public static function toConstantString($level = null, $phpVer = null, $explicitStrict = true)
    {
        $string = '';
        $level = $level === null
            ? \error_reporting()
            : $level;
        $allConstants = self::getConstants($phpVer); // includes E_ALL
        $levelConstants = self::filterConstantsByLevel($allConstants, $level); // excludes E_ALL
        $eAll = $allConstants['E_ALL'];
        unset($allConstants['E_ALL']);
        if (\count($levelConstants) > \count($allConstants) / 2) {
            $string = 'E_ALL';
            foreach ($allConstants as $constantName => $value) {
                $isExplicit = $explicitStrict
                    && $constantName == 'E_STRICT';
                if (self::inBitmask($value, $level)) {
                    if (!self::inBitmask($value, $eAll) || $isExplicit) {
                        // only thing that wouldn't be in E_ALL is E_STRICT
                        $string .= ' | ' . $constantName;
                    }
                } else {
                    if (self::inBitmask($value, $eAll) || $isExplicit) {
                        $string .= ' & ~' . $constantName;
                    }
                }
            }
        } else {
            $string = \implode(' | ', \array_keys($levelConstants));
        }
        return $string ?: '0';
    }
[toConstantString description]

@param integer $level          Error Level (bitmask) value
@param string  $phpVer         (PHP_VERSION) php Version
@param boolean $explicitStrict (true) if level === E_ALL, always include/exclude E_STRICT for disambiguation / portability

@return string