ctype_alpha - PHP code example

The PHP Function ctype_alpha

PHP’s character type functions offer developers an efficient way to validate and filter string input, ensuring that they only process valid data. In this article, we’ll explore a variety of functions, including the ctype_alpha function, which checks whether a string is alphabetic.

The ctype_alpha function is an in-built PHP function which verifies if the given string contains only alphabets (a-z, upper and lower case). This function returns True if the string does not contain any non-alphabet characters, and False otherwise.

Note: The ctype_alpha() function works only if you have the ctype extension enabled, which is the default for all modern versions of PHP (it’s also available as a separate compile-time option). Also, remember that passing an argument as an integer will cause the function to return a string, so it’s usually best to cast the argument to a string first, unless you want to check something other than the ASCII codepoints of the character.

This function works for strings containing any character in the ASCII range, but it won’t work for hex characters, which are not alphabetic in the standard C locale. For example, the string 123ABc will not pass the test because it includes a hex character. For this reason, the ctype_alpha function should always be used in conjunction with other string verification functions to verify that all of the strings are alphabetic or numeric, if you want to ensure that your application is safe from hackers. To learn more about PHP’s string functions, check out our complete PHP String Reference.

ctype_alpha example

        return $filepaths;
    }

    /** * Returns whether the file path is an absolute path. */
    private function isAbsolutePath(string $file): bool
    {
        if ('/' === $file[0] || '\\' === $file[0]
            || (\strlen($file) > 3 && ctype_alpha($file[0])
                && ':' === $file[1]
                && ('\\' === $file[2] || '/' === $file[2])
            )
            || null !== parse_url($file, \PHP_URL_SCHEME)
        ) {
            return true;
        }

        return false;
    }
}

if (!$this->isAbsolutePath($endPath)) {
            throw new InvalidArgumentException(sprintf('The end path "%s" is not absolute.', $endPath));
        }

        // Normalize separators on Windows         if ('\\' === \DIRECTORY_SEPARATOR) {
            $endPath = str_replace('\\', '/', $endPath);
            $startPath = str_replace('\\', '/', $startPath);
        }

        $splitDriveLetter = fn ($path) => (\strlen($path) > 2 && ':' === $path[1] && '/' === $path[2] && ctype_alpha($path[0]))
            ? [substr($path, 2), strtoupper($path[0])]
            : [$path, null];

        $splitPath = function D$path) {
            $result = [];

            foreach (explode('/', trim($path, '/')) as $segment) {
                if ('..' === $segment) {
                    array_pop($result);
                } elseif ('.' !== $segment && '' !== $segment) {
                    $result[] = $segment;
                }

        return filemtime((string) $storage) < $time;
    }

    /** * Returns true if the file is an existing absolute path. */
    protected static function isAbsolutePath(string $file): bool
    {
        if ('/' == $file[0] || '\\' == $file[0]
            || (\strlen($file) > 3 && ctype_alpha($file[0])
                && ':' == $file[1]
                && ('\\' == $file[2] || '/' == $file[2])
            )
            || null !== parse_url($file, \PHP_URL_SCHEME)
        ) {
            return true;
        }

        return false;
    }
}

$this->context->buildViolation($constraint->message)
                ->setParameter('{{ value }}', $this->formatValue($value))
                ->setCode(Iban::INVALID_CHARACTERS_ERROR)
                ->addViolation();

            return;
        }

        // ...start with a two-letter country code         $countryCode = substr($canonicalized, 0, 2);

        if (!ctype_alpha($countryCode)) {
            $this->context->buildViolation($constraint->message)
                ->setParameter('{{ value }}', $this->formatValue($value))
                ->setCode(Iban::INVALID_COUNTRY_CODE_ERROR)
                ->addViolation();

            return;
        }

        // ...have a format available         if (!\array_key_exists($countryCode, self::FORMATS)) {
            $this->context->buildViolation($constraint->message)

/** * Format validation Rules. */
class FormatRules
{
    /** * Alpha */
    public function alpha(?string $str = null): bool
    {
        return ctype_alpha($str ?? '');
    }

    /** * Alpha with spaces. * * @param string|null $value Value. * * @return bool True if alpha with spaces, else false. */
    public function alpha_space(?string $value = null): bool
    {

if ($value[0] === '"') {
            $value = str_replace('""', '"', substr($value, 1, strlen($value) - 2));

            return self::T_STRING;
        }

        if (isset($this->noCase[$value])) {
            return $this->noCase[$value];
        }

        if ($value[0] === '_' || $value[0] === '\\' || ctype_alpha($value[0])) {
            return self::T_IDENTIFIER;
        }

        $lowerValue = strtolower($value);

        if (isset($this->withCase[$lowerValue])) {
            return $this->withCase[$lowerValue];
        }

        // Checking numeric value         if (is_numeric($value)) {

array_keys($this->env->getBinaryOperators())
        );

        $operators = array_combine($operators, array_map('strlen', $operators));
        arsort($operators);

        $regex = [];
        foreach ($operators as $operator => $length) {
            // an operator that ends with a character must be followed by             // a whitespace, a parenthesis, an opening map [ or sequence {             $r = preg_quote($operator, '/');
            if (ctype_alpha($operator[$length - 1])) {
                $r .= '(?=[\s()\[{])';
            }

            // an operator that begins with a character must not have a dot or pipe before             if (ctype_alpha($operator[0])) {
                $r = '(?<![\.\|])'.$r;
            }

            // an operator with a space can be any amount of whitespaces             $r = preg_replace('/\s+/', '\s+', $r);

$extras = [];

        // Discover the name of the script part of the locale         // i.e. in zh_Hans_MO, "Hans" is the script         if ($script = \Locale::getScript($locale)) {
            $extras[] = str_replace(['(', ')'], ['[', ']'], $reader->readEntry($tempDir.'/lang', $displayLocale, ['Scripts', $script]));
        }

        // Discover the name of the region part of the locale         // i.e. in de_AT, "AT" is the region         if ($region = \Locale::getRegion($locale)) {
            if (ctype_alpha($region) && !RegionDataGenerator::isValidCountryCode($region)) {
                throw new MissingResourceException(sprintf('Skipping "%s" due an invalid country.', $locale));
            }

            $extras[] = str_replace(['(', ')'], ['[', ']'], $reader->readEntry($tempDir.'/region', $displayLocale, ['Countries', $region]));
        }

        if ($extras) {
            $extra = array_shift($extras);
            foreach ($extras as $part) {
                $extra = str_replace(['{0}', '{1}'], [$extra,  $part], $separator);
            }

// must contain alphanumeric values only         if (!ctype_alnum($canonicalize)) {
            $this->context->buildViolation($constraint->message)
                ->setParameter('{{ value }}', $this->formatValue($value))
                ->setCode(Bic::INVALID_CHARACTERS_ERROR)
                ->addViolation();

            return;
        }

        // first 4 letters must be alphabetic (bank code)         if (!ctype_alpha(substr($canonicalize, 0, 4))) {
            $this->context->buildViolation($constraint->message)
                ->setParameter('{{ value }}', $this->formatValue($value))
                ->setCode(Bic::INVALID_BANK_CODE_ERROR)
                ->addViolation();

            return;
        }

        $bicCountryCode = substr($canonicalize, 4, 2);
        if (!isset(self::BIC_COUNTRY_TO_IBAN_COUNTRY_MAP[$bicCountryCode]) && !Countries::exists($bicCountryCode)) {
            $this->context->buildViolation($constraint->message)

if (false === $dirSeparatorPosition = strrpos($path, '/')) {
            return '';
        }

        // Directory equals root directory "/"         if (0 === $dirSeparatorPosition) {
            return $scheme.'/';
        }

        // Directory equals Windows root "C:/"         if (2 === $dirSeparatorPosition && ctype_alpha($path[0]) && ':' === $path[1]) {
            return $scheme.substr($path, 0, 3);
        }

        return $scheme.substr($path, 0, $dirSeparatorPosition);
    }

    /** * Returns canonical path of the user's home directory. * * Supported operating systems: * * - UNIX * - Windows8 and upper * * If your operating system or environment isn't supported, an exception is thrown. * * The result is a canonical path. * * @throws RuntimeException If your operating system or environment isn't supported */

$operators = ['not', '!', 'or', '||', '&&', 'and', '|', '^', '&', '==', '===', '!=', '!==', '<', '>', '>=', '<=', 'not in', 'in', '..', '+', '-', '~', '*', '/', '%', 'contains', 'starts with', 'ends with', 'matches', '**'];
$operators = array_combine($operators, array_map('strlen', $operators));
arsort($operators);

$regex = [];
foreach ($operators as $operator => $length) {
    // Collisions of character operators:     // - an operator that begins with a character must have a space or a parenthesis before or starting at the beginning of a string     // - an operator that ends with a character must be followed by a whitespace or a parenthesis     $regex[] =
        (ctype_alpha($operator[0]) ? '(?<=^|[\s(])' : '')
        .preg_quote($operator, '/')
        .(ctype_alpha($operator[$length - 1]) ? '(?=[\s(])' : '');
}

echo '/'.implode('|', $regex).'/A';

            if ($level < 0) {
                throw new LoaderError(sprintf('Looks like you try to load a template outside configured directories (%s).', $name));
            }
        }
    }

    private function isAbsolutePath(string $file): bool
    {
        return strspn($file, '/\\', 0, 1)
            || (\strlen($file) > 3 && ctype_alpha($file[0])
                && ':' === $file[1]
                && strspn($file, '/\\', 2, 1)
            )
            || null !== parse_url($file, \PHP_URL_SCHEME)
        ;
    }
}

private function getRelativePath(string $path): string
    {
        if (null !== $this->projectDir && str_starts_with($path, $this->projectDir)) {
            return ltrim(substr($path, \strlen($this->projectDir)), \DIRECTORY_SEPARATOR);
        }

        return $path;
    }

    private function isAbsolutePath(string $file): bool
    {
        return strspn($file, '/\\', 0, 1) || (\strlen($file) > 3 && ctype_alpha($file[0]) && ':' === $file[1] && strspn($file, '/\\', 2, 1)) || null !== parse_url($file, \PHP_URL_SCHEME);
    }

    /** * @return FilesystemLoader[] */
    private function getFilesystemLoaders(): array
    {
        if (isset($this->filesystemLoaders)) {
            return $this->filesystemLoaders;
        }
        $this->filesystemLoaders = [];

use Symfony\Polyfill\Ctype as p;

if (\PHP_VERSION_ID >= 80000) {
    return require __DIR__.'/bootstrap80.php';
}

if (!function_exists('ctype_alnum')) {
    function ctype_alnum($text) { return p\Ctype::ctype_alnum($text); }
}
if (!function_exists('ctype_alpha')) {
    function ctype_alpha($text) { return p\Ctype::ctype_alpha($text); }
}
if (!function_exists('ctype_cntrl')) {
    function ctype_cntrl($text) { return p\Ctype::ctype_cntrl($text); }
}
if (!function_exists('ctype_digit')) {
    function ctype_digit($text) { return p\Ctype::ctype_digit($text); }
}
if (!function_exists('ctype_graph')) {
    function ctype_graph($text) { return p\Ctype::ctype_graph($text); }
}
if (!function_exists('ctype_lower')) {