is_string - PHP code example

The Is_String Function in PHP

The is_string function in php verifies whether or not the value of a variable is a string type. It takes one parameter, which is the variable to be checked and returns a boolean value of true when the variable in question is a string and false otherwise. It is important to understand how to use this function, especially when writing code that handles different types of data.

PHP is a loosely-typed language, meaning that variables are not declared with their type, and the PHP interpreter will try to infer the correct type for the given value of a variable. However, there are some situations where this is not enough. For example, an array is a variable that can store elements of different types, including integers, objects, and strings. Using the is_array function in these cases can help ensure that your code works correctly.

Another important function for checking the type of a variable is var_dump(), which displays the details of the given variable, which can be helpful when debugging. Other useful functions include strlen(str) to return the length of a string, substr(str[start], length) to return a substring, and strtoupper(str) and strtolower(str) to convert a string to uppercase or lowercase.

There are also some special string functions, such as explode(str[start], length) which tokenizes a string into an array, and shuffle(array) to sort its elements in reverse order. Moreover, the string 'FALSE' is evaluated to boolean TRUE in PHP, which can be useful if you need to represent boolean values as strings (e.g. in HTML select> or radio buttons' values).

is_string example

  public function renderResponse(array $main_content, Request $request, RouteMatchInterface $route_match) {
    $response = new AjaxResponse();

    if (isset($main_content['#type']) && ($main_content['#type'] == 'ajax')) {
      // Complex Ajax callbacks can return a result that contains an error       // message or a specific set of commands to send to the browser.       $main_content += $this->elementInfoManager->getInfo('ajax');
      $error = $main_content['#error'];
      if (!empty($error)) {
        // Fall back to some default message otherwise use the specific one.         if (!is_string($error)) {
          $error = 'An error occurred while handling the request: The server received invalid input.';
        }
        $response->addCommand(new AlertCommand($error));
      }
    }

    $html = $this->renderer->renderRoot($main_content);
    $response->setAttachments($main_content['#attached']);

    // The selector for the insert command is NULL as the new content will     // replace the element making the Ajax call. The default 'replaceWith'

'field_name' => $row->getSourceProperty('field_name')],
        $this->t('Widget types @types are used in Drupal 6 field instances: widget type @selected_type applied to the Drupal 8 base field', [
          '@types' => implode(', ', $widget_types),
          '@selected_type' => $widget_types[0],
        ])
      );
    }

    // Unserialize data.     $global_settings = unserialize($row->getSourceProperty('global_settings'));
    $db_columns = $row->getSourceProperty('db_columns');
    $db_columns = is_string($db_columns) ? unserialize($db_columns) : FALSE;
    $row->setSourceProperty('global_settings', $global_settings);
    $row->setSourceProperty('db_columns', $db_columns);
    return parent::prepareRow($row);
  }

  /** * {@inheritdoc} */
  public function getIds() {
    $ids['field_name'] = [
      'type' => 'string',

if (($date !== null) and !is_array($date)  and !($date instanceof Zend_Date) and !defined($date) and Zend_Locale::isLocale($date, true, false)) {
            $locale = $date;
            $date   = null;
            $part   = null;
        } else if (($part !== null) and !defined($part) and Zend_Locale::isLocale($part, true, false)) {
            $locale = $part;
            $part   = null;
        }

        $this->setLocale($locale);
        if (is_string($date) && ($part === null) && (strlen($date) <= 5)) {
            $part = $date;
            $date = null;
        }

        if ($date === null) {
            if ($part === null) {
                $date = time();
            } else if ($part !== self::TIMESTAMP) {
                $date = self::now($locale);
                $date = $date->get($part);
            }
        }

        return $fields;
    }

    /** * @param array<mixed> $ids */
    private function validateIds(array $ids): void
    {
        foreach ($ids as $id) {
            if (!\is_string($id) && !\is_array($id)) {
                throw DataAbstractionLayerException::invalidCriteriaIds($ids, 'Ids should be a list of strings or a list of key value pairs, for entities with combined primary keys');
            }

            if (!\is_array($id)) {
                continue;
            }

            foreach ($id as $key => $value) {
                if (!\is_string($key) || !\is_string($value)) {
                    throw DataAbstractionLayerException::invalidCriteriaIds($ids, 'Ids should be a list of strings or a list of key value pairs, for entities with combined primary keys');
                }
            }

    /** * Renders the string conversion of the value. */
    private function writeValue(mixed $value): string
    {
        if ('%%%%not_defined%%%%' === $value) {
            return '';
        }

        if (\is_string($value) || is_numeric($value)) {
            return $value;
        }

        if (false === $value) {
            return 'false';
        }

        if (true === $value) {
            return 'true';
        }

    public function __construct(array $options)
    {
        $options = array_merge(
            ['criteria' => new Criteria()],
            $options
        );

        if (!\is_string($options['entity'] ?? null)) {
            throw new MissingOptionsException(sprintf('Option "entity" must be given for constraint %s', self::class), ['entity']);
        }

        if (!($options['context'] ?? null) instanceof Context) {
            throw new MissingOptionsException(sprintf('Option "context" must be given for constraint %s', self::class), ['context']);
        }

        if (!($options['criteria'] ?? null) instanceof Criteria) {
            throw new InvalidOptionsException(sprintf('Option "criteria" must be an instance of Shopware\Core\Framework\DataAbstractionLayer\Search\Criteria for constraint %s', self::class), ['criteria']);
        }

      // perform index normalization.       $schema['fields'] = $entity_schema[$table_name]['fields'];

      foreach ($index_keys as $key => $add_method) {
        if (!empty($schema[$key])) {
          foreach ($schema[$key] as $name => $specifier) {
            // If a set of field columns were specified we process only indexes             // involving them. Only indexes for which all columns exist are             // actually created.             $create = FALSE;
            $specifier_columns = array_map(function D$item) {
              return is_string($item) ? $item : reset($item);
            }, $specifier);
            if (!isset($column_names) || array_intersect($specifier_columns, $column_names)) {
              $create = TRUE;
              foreach ($specifier_columns as $specifier_column_name) {
                // This may happen when adding more than one field in the same                 // update run. Eventually when all field columns have been                 // created the index will be created too.                 if (!$schema_handler->fieldExists($table_name, $specifier_column_name)) {
                  $create = FALSE;
                  break;
                }
              }

    public const DEFAULT_ENCODING_OPTIONS = 15;

    protected $encodingOptions = self::DEFAULT_ENCODING_OPTIONS;

    /** * @param bool $json If the data is already a JSON string */
    public function __construct(mixed $data = null, int $status = 200, array $headers = [], bool $json = false)
    {
        parent::__construct('', $status, $headers);

        if ($json && !\is_string($data) && !is_numeric($data) && !\is_callable([$data, '__toString'])) {
            throw new \TypeError(sprintf('"%s": If $json is set to true, argument $data must be a string or object implementing __toString(), "%s" given.', __METHOD__, get_debug_type($data)));
        }

        $data ??= new \ArrayObject();

        $json ? $this->setJson($data) : $this->setData($data);
    }

    /** * Factory method for chainability. * * Example: * * return JsonResponse::fromJsonString('{"key": "value"}') * ->setSharedMaxAge(300); * * @param string $data The JSON response string * @param int $status The response status code (200 "OK" by default) * @param array $headers An array of response headers */

public function replaceMatches(string $fromRegexp, string|callable $to): static
    {
        if ($this->ignoreCase) {
            $fromRegexp .= 'i';
        }

        if (\is_array($to) || $to instanceof \Closure) {
            $replace = 'preg_replace_callback';
            $to = static function Darray $m) use ($to): string {
                $to = $to($m);

                if ('' !== $to && (!\is_string($to) || !preg_match('//u', $to))) {
                    throw new InvalidArgumentException('Replace callback must return a valid UTF-8 string.');
                }

                return $to;
            };
        } elseif ('' !== $to && !preg_match('//u', $to)) {
            throw new InvalidArgumentException('Invalid UTF-8 string.');
        } else {
            $replace = 'preg_replace';
        }

T USE THIS FUNCTION OUTSIDE ITS INTENDED SCOPE
     *
     * @internal
     */
    public static function escapeFunction(mixed $parameter): string
    {
        $result = $parameter;

        switch (true) {
            // Check if result is non-unicode string using PCRE_UTF8 modifier             case \is_string($result) && !preg_match('//u', $result):
                $result = '0x' . strtoupper(bin2hex($result));

                break;

            case \is_string($result):
                $result = '\'' . addslashes($result) . '\'';

                break;

            case \is_array($result):
                foreach ($result as &$value) {

        $value = apply_filters( "customize_sanitize_js_{$this->id}", $this->value(), $this );

        if ( is_string( $value ) ) {
            return html_entity_decode( $value, ENT_QUOTES, 'UTF-8' );
        }

        return $value;
    }

    /** * Retrieves the data to export to the client via JSON. * * @since 4.6.0 * * @return array Array of parameters passed to JavaScript. */

private ?\DateTimeImmutable $from;
    private \DateTimeImmutable $until;
    private \DatePeriod $period;
    private string $description;
    private string|int|float|\DateInterval $interval;

    public function __construct(
        string|int|float|\DateInterval $interval,
        string|\DateTimeImmutable $from = null,
        string|\DateTimeImmutable $until = new \DateTimeImmutable('3000-01-01'),
    ) {
        $this->from = \is_string($from) ? new \DateTimeImmutable($from) : $from;
        $this->until = \is_string($until) ? new \DateTimeImmutable($until) : $until;

        if (\is_int($interval) || \is_float($interval)) {
            if (0 >= $interval) {
                throw new InvalidArgumentException('The "$interval" argument must be greater than zero.');
            }

            $this->intervalInSeconds = $interval;
            $this->description = sprintf('every %d seconds', $this->intervalInSeconds);

            return;
        }

if (-1 === $depth) {
            AbstractDumper::dumpLine(0);
        }
        AbstractDumper::dumpLine($depth);
    }

    private function getSourceLink(string $file, int $line): string|false
    {
        $options = $this->extraDisplayOptions + $this->displayOptions;

        if ($fmt = $options['fileLinkFormat']) {
            return \is_string($fmt) ? strtr($fmt, ['%f' => $file, '%l' => $line]) : $fmt->format($file, $line);
        }

        return false;
    }
}

function esc(string $str): string
{
    return htmlspecialchars($str, \ENT_QUOTES, 'UTF-8');
}

use Symfony\Component\Cache\Marshaller\MarshallerInterface;

/** * @author Ahmed TAILOULOUTE <ahmed.tailouloute@gmail.com> */
class IdentityMarshaller implements MarshallerInterface
{
    public function marshall(array $values, ?array &$failed): array
    {
        foreach ($values as $key => $value) {
            if (!\is_string($value)) {
                throw new \LogicException(sprintf('%s accepts only string as data.', __METHOD__));
            }
        }

        return $values;
    }

    public function unmarshall(string $value): string
    {
        return $value;
    }
}

protected function setType($type) {
    if ($type) {
      $this->type = $type;
    }
  }

  /** * {@inheritdoc} */
  public function getFormState(ViewEntityInterface $view, $display_id, $js) {
    // $js may already have been converted to a Boolean.     $ajax = is_string($js) ? $js === 'ajax' : $js;
    return (new FormState())
      ->set('form_id', $this->getFormId())
      ->set('form_key', $this->getFormKey())
      ->set('ajax', $ajax)
      ->set('display_id', $display_id)
      ->set('view', $view)
      ->set('type', $this->type)
      ->set('id', $this->id)
      ->disableRedirect()
      ->addBuildInfo('callback_object', $this);
  }