SSL, otherwise false.
 */
function is_ssl() {
	if ( isset( $_SERVER['HTTPS'] ) ) {
		if ( 'on' === strtolower( $_SERVER['HTTPS'] ) ) {
			return true;
		}

		if ( '1' === (string) $_SERVER['HTTPS'] ) {
			return true;
		}
	} elseif ( isset( $_SERVER['SERVER_PORT'] ) && ( '443' === (string) $_SERVER['SERVER_PORT'] ) ) {
		return true;
	}

	return false;
}

/**
 * Converts a shorthand byte value to an integer byte value.
 *
 * @since 2.3.0
 * @since 4.6.0 Moved from media.php to load.php.
 *
 * @link https://www.php.net/manual/en/function.ini-get.php
 * @link https://www.php.net/manual/en/faq.using.php#faq.using.shorthandbytes
 *
 * @param string $value A (PHP ini) byte value, either shorthand or ordinary.
 * @return int An integer byte value.
 */
function wp_convert_hr_to_bytes( $value ) {
	$value = strtolower( trim( $value ) );
	$bytes = (int) $value;

	if ( str_contains( $value, 'g' ) ) {
		$bytes *= GB_IN_BYTES;
	} elseif ( str_contains( $value, 'm' ) ) {
		$bytes *= MB_IN_BYTES;
	} elseif ( str_contains( $value, 'k' ) ) {
		$bytes *= KB_IN_BYTES;
	}

	// Deal with large (float) values which run into the maximum integer size.
	return min( $bytes, PHP_INT_MAX );
}

/**
 * Determines whether a PHP ini value is changeable at runtime.
 *
 * @since 4.6.0
 *
 * @link https://www.php.net/manual/en/function.ini-get-all.php
 *
 * @param string $setting The name of the ini setting to check.
 * @return bool True if the value is changeable at runtime. False otherwise.
 */
function wp_is_ini_value_changeable( $setting ) {
	static $ini_all;

	if ( ! isset( $ini_all ) ) {
		$ini_all = false;
		// Sometimes `ini_get_all()` is disabled via the `disable_functions` option for "security purposes".
		if ( function_exists( 'ini_get_all' ) ) {
			$ini_all = ini_get_all();
		}
	}

	// Bit operator to workaround https://bugs.php.net/bug.php?id=44936 which changes access level to 63 in PHP 5.2.6 - 5.2.17.
	if ( isset( $ini_all[ $setting ]['access'] )
		&& ( INI_ALL === ( $ini_all[ $setting ]['access'] & 7 ) || INI_USER === ( $ini_all[ $setting ]['access'] & 7 ) )
	) {
		return true;
	}

	// If we were unable to retrieve the details, fail gracefully to assume it's changeable.
	if ( ! is_array( $ini_all ) ) {
		return true;
	}

	return false;
}

/**
 * Determines whether the current request is a WordPress Ajax request.
 *
 * @since 4.7.0
 *
 * @return bool True if it's a WordPress Ajax request, false otherwise.
 */
function wp_doing_ajax() {
	/**
	 * Filters whether the current request is a WordPress Ajax request.
	 *
	 * @since 4.7.0
	 *
	 * @param bool $wp_doing_ajax Whether the current request is a WordPress Ajax request.
	 */
	return apply_filters( 'wp_doing_ajax', defined( 'DOING_AJAX' ) && DOING_AJAX );
}

/**
 * Determines whether the current request should use themes.
 *
 * @since 5.1.0
 *
 * @return bool True if themes should be used, false otherwise.
 */
function wp_using_themes() {
	/**
	 * Filters whether the current request should use themes.
	 *
	 * @since 5.1.0
	 *
	 * @param bool $wp_using_themes Whether the current request should use themes.
	 */
	return apply_filters( 'wp_using_themes', defined( 'WP_USE_THEMES' ) && WP_USE_THEMES );
}

/**
 * Determines whether the current request is a WordPress cron request.
 *
 * @since 4.8.0
 *
 * @return bool True if it's a WordPress cron request, false otherwise.
 */
function wp_doing_cron() {
	/**
	 * Filters whether the current request is a WordPress cron request.
	 *
	 * @since 4.8.0
	 *
	 * @param bool $wp_doing_cron Whether the current request is a WordPress cron request.
	 */
	return apply_filters( 'wp_doing_cron', defined( 'DOING_CRON' ) && DOING_CRON );
}

/**
 * Checks whether the given variable is a WordPress Error.
 *
 * Returns whether `$thing` is an instance of the `WP_Error` class.
 *
 * @since 2.1.0
 *
 * @param mixed $thing The variable to check.
 * @return bool Whether the variable is an instance of WP_Error.
 */
function is_wp_error( $thing ) {
	$is_wp_error = ( $thing instanceof WP_Error );

	if ( $is_wp_error ) {
		/**
		 * Fires when `is_wp_error()` is called and its parameter is an instance of `WP_Error`.
		 *
		 * @since 5.6.0
		 *
		 * @param WP_Error $thing The error object passed to `is_wp_error()`.
		 */
		do_action( 'is_wp_error_instance', $thing );
	}

	return $is_wp_error;
}

/**
 * Determines whether file modifications are allowed.
 *
 * @since 4.8.0
 *
 * @param string $context The usage context.
 * @return bool True if file modification is allowed, false otherwise.
 */
function wp_is_file_mod_allowed( $context ) {
	/**
	 * Filters whether file modifications are allowed.
	 *
	 * @since 4.8.0
	 *
	 * @param bool   $file_mod_allowed Whether file modifications are allowed.
	 * @param string $context          The usage context.
	 */
	return apply_filters( 'file_mod_allowed', ! defined( 'DISALLOW_FILE_MODS' ) || ! DISALLOW_FILE_MODS, $context );
}

/**
 * Starts scraping edited file errors.
 *
 * @since 4.9.0
 */
function wp_start_scraping_edited_file_errors() {
	if ( ! isset( $_REQUEST['wp_scrape_key'] ) || ! isset( $_REQUEST['wp_scrape_nonce'] ) ) {
		return;
	}

	$key   = substr( sanitize_key( wp_unslash( $_REQUEST['wp_scrape_key'] ) ), 0, 32 );
	$nonce = wp_unslash( $_REQUEST['wp_scrape_nonce'] );

	if ( get_transient( 'scrape_key_' . $key ) !== $nonce ) {
		echo "###### wp_scraping_result_start:$key ######";
		echo wp_json_encode(
			array(
				'code'    => 'scrape_nonce_failure',
				'message' => __( 'Scrape key check failed. Please try again.' ),
			)
		);
		echo "###### wp_scraping_result_end:$key ######";
		die();
	}

	if ( ! defined( 'WP_SANDBOX_SCRAPING' ) ) {
		define( 'WP_SANDBOX_SCRAPING', true );
	}

	register_shutdown_function( 'wp_finalize_scraping_edited_file_errors', $key );
}

/**
 * Finalizes scraping for edited file errors.
 *
 * @since 4.9.0
 *
 * @param string $scrape_key Scrape key.
 */
function wp_finalize_scraping_edited_file_errors( $scrape_key ) {
	$error = error_get_last();

	echo "\n###### wp_scraping_result_start:$scrape_key ######\n";

	if ( ! empty( $error )
		&& in_array( $error['type'], array( E_CORE_ERROR, E_COMPILE_ERROR, E_ERROR, E_PARSE, E_USER_ERROR, E_RECOVERABLE_ERROR ), true )
	) {
		$error = str_replace( ABSPATH, '', $error );
		echo wp_json_encode( $error );
	} else {
		echo wp_json_encode( true );
	}

	echo "\n###### wp_scraping_result_end:$scrape_key ######\n";
}

/**
 * Checks whether current request is a JSON request, or is expecting a JSON response.
 *
 * @since 5.0.0
 *
 * @return bool True if `Accepts` or `Content-Type` headers contain `application/json`.
 *              False otherwise.
 */
function wp_is_json_request() {
	if ( isset( $_SERVER['HTTP_ACCEPT'] ) && wp_is_json_media_type( $_SERVER['HTTP_ACCEPT'] ) ) {
		return true;
	}

	if ( isset( $_SERVER['CONTENT_TYPE'] ) && wp_is_json_media_type( $_SERVER['CONTENT_TYPE'] ) ) {
		return true;
	}

	return false;
}

/**
 * Checks whether current request is a JSONP request, or is expecting a JSONP response.
 *
 * @since 5.2.0
 *
 * @return bool True if JSONP request, false otherwise.
 */
function wp_is_jsonp_request() {
	if ( ! isset( $_GET['_jsonp'] ) ) {
		return false;
	}

	if ( ! function_exists( 'wp_check_jsonp_callback' ) ) {
		require_once ABSPATH . WPINC . '/functions.php';
	}

	$jsonp_callback = $_GET['_jsonp'];
	if ( ! wp_check_jsonp_callback( $jsonp_callback ) ) {
		return false;
	}

	/** This filter is documented in wp-includes/rest-api/class-wp-rest-server.php */
	$jsonp_enabled = apply_filters( 'rest_jsonp_enabled', true );

	return $jsonp_enabled;
}

/**
 * Checks whether a string is a valid JSON Media Type.
 *
 * @since 5.6.0
 *
 * @param string $media_type A Media Type string to check.
 * @return bool True if string is a valid JSON Media Type.
 */
function wp_is_json_media_type( $media_type ) {
	static $cache = array();

	if ( ! isset( $cache[ $media_type ] ) ) {
		$cache[ $media_type ] = (bool) preg_match( '/(^|\s|,)application\/([\w!#\$&-\^\.\+]+\+)?json(\+oembed)?($|\s|;|,)/i', $media_type );
	}

	return $cache[ $media_type ];
}

/**
 * Checks whether current request is an XML request, or is expecting an XML response.
 *
 * @since 5.2.0
 *
 * @return bool True if `Accepts` or `Content-Type` headers contain `text/xml`
 *              or one of the related MIME types. False otherwise.
 */
function wp_is_xml_request() {
	$accepted = array(
		'text/xml',
		'application/rss+xml',
		'application/atom+xml',
		'application/rdf+xml',
		'text/xml+oembed',
		'application/xml+oembed',
	);

	if ( isset( $_SERVER['HTTP_ACCEPT'] ) ) {
		foreach ( $accepted as $type ) {
			if ( str_contains( $_SERVER['HTTP_ACCEPT'], $type ) ) {
				return true;
			}
		}
	}

	if ( isset( $_SERVER['CONTENT_TYPE'] ) && in_array( $_SERVER['CONTENT_TYPE'], $accepted, true ) ) {
		return true;
	}

	return false;
}

/**
 * Checks if this site is protected by HTTP Basic Auth.
 *
 * At the moment, this merely checks for the present of Basic Auth credentials. Therefore, calling
 * this function with a context different from the current context may give inaccurate results.
 * In a future release, this evaluation may be made more robust.
 *
 * Currently, this is only used by Application Passwords to prevent a conflict since it also utilizes
 * Basic Auth.
 *
 * @since 5.6.1
 *
 * @global string $pagenow The filename of the current screen.
 *
 * @param string $context The context to check for protection. Accepts 'login', 'admin', and 'front'.
 *                        Defaults to the current context.
 * @return bool Whether the site is protected by Basic Auth.
 */
function wp_is_site_protected_by_basic_auth( $context = '' ) {
	global $pagenow;

	if ( ! $context ) {
		if ( 'wp-login.php' === $pagenow ) {
			$context = 'login';
		} elseif ( is_admin() ) {
			$context = 'admin';
		} else {
			$context = 'front';
		}
	}

	$is_protected = ! empty( $_SERVER['PHP_AUTH_USER'] ) || ! empty( $_SERVER['PHP_AUTH_PW'] );

	/**
	 * Filters whether a site is protected by HTTP Basic Auth.
	 *
	 * @since 5.6.1
	 *
	 * @param bool $is_protected Whether the site is protected by Basic Auth.
	 * @param string $context    The context to check for protection. One of 'login', 'admin', or 'front'.
	 */
	return apply_filters( 'wp_is_site_protected_by_basic_auth', $is_protected, $context );
}
<br />
<b>Fatal error</b>:  Uncaught Error: Call to undefined function wp_check_php_mysql_versions() in /home/kordian1/domains/ostrabrama.pl/public_html/wp-settings.php:38
Stack trace:
#0 /home/kordian1/domains/ostrabrama.pl/public_html/wp-config.php(81): require_once()
#1 /home/kordian1/domains/ostrabrama.pl/public_html/wp-load.php(50): require_once('/home/kordian1/...')
#2 /home/kordian1/domains/ostrabrama.pl/public_html/wp-blog-header.php(13): require_once('/home/kordian1/...')
#3 /home/kordian1/domains/ostrabrama.pl/public_html/index.php(17): require('/home/kordian1/...')
#4 {main}
  thrown in <b>/home/kordian1/domains/ostrabrama.pl/public_html/wp-settings.php</b> on line <b>38</b><br />