PhpCsFixer\Fixer\Casing\NativeFunctionCasingFixer::fix PHP Method

    public function fix(\SplFileInfo $file, Tokens $tokens)
    {
        static $nativeFunctionNames = null;
        if (null === $nativeFunctionNames) {
            $nativeFunctionNames = $this->getNativeFunctionNames();
        }
        for ($index = 0, $count = $tokens->count(); $index < $count; ++$index) {
            // test if we are at a function all
            if (!$tokens[$index]->isGivenKind(T_STRING)) {
                continue;
            }
            $next = $tokens->getNextMeaningfulToken($index);
            if (!$tokens[$next]->equals('(')) {
                $index = $next;
                continue;
            }
            $functionNamePrefix = $tokens->getPrevMeaningfulToken($index);
            if ($tokens[$functionNamePrefix]->isGivenKind(array(T_DOUBLE_COLON, T_NEW, T_OBJECT_OPERATOR, T_FUNCTION))) {
                continue;
            }
            if ($tokens[$functionNamePrefix]->isGivenKind(T_NS_SEPARATOR)) {
                // skip if the call is to a constructor or to a function in a namespace other than the default
                $prev = $tokens->getPrevMeaningfulToken($functionNamePrefix);
                if ($tokens[$prev]->isGivenKind(array(T_STRING, T_NEW))) {
                    continue;
                }
            }
            // test if the function call is to a native PHP function
            $lower = strtolower($tokens[$index]->getContent());
            if (!array_key_exists($lower, $nativeFunctionNames)) {
                continue;
            }
            $tokens[$index]->setContent($nativeFunctionNames[$lower]);
            $index = $next;
        }
    }