upload files in form wp code example

Example: wp_import_upload_form

function wp_import_upload_form( $action ) {

	/**
	 * Filters the maximum allowed upload size for import files.
	 *
	 * @since 2.3.0
	 *
	 * @see wp_max_upload_size()
	 *
	 * @param int $max_upload_size Allowed upload size. Default 1 MB.
	 */
	$bytes      = apply_filters( 'import_upload_size_limit', wp_max_upload_size() );
	$size       = size_format( $bytes );
	$upload_dir = wp_upload_dir();
	if ( ! empty( $upload_dir['error'] ) ) :
		?>
		<div class="error"><p><?php _e( 'Before you can upload your import file, you will need to fix the following error:' ); ?></p>
		<p><strong><?php echo $upload_dir['error']; ?></strong></p></div>
								<?php
	else :
		?>
<form enctype="multipart/form-data" id="import-upload-form" method="post" class="wp-upload-form" action="<?php echo esc_url( wp_nonce_url( $action, 'import-upload' ) ); ?>">
<p>
		<?php
		printf(
			'<label for="upload">%s</label> (%s)',
			__( 'Choose a file from your computer:' ),
			/* translators: %s: Maximum allowed file size. */
			sprintf( __( 'Maximum size: %s' ), $size )
		);
		?>
<input type="file" id="upload" name="import" size="25" />
<input type="hidden" name="action" value="save" />
<input type="hidden" name="max_file_size" value="<?php echo $bytes; ?>" />
</p>
		<?php submit_button( __( 'Upload file and import' ), 'primary' ); ?>
</form>
		<?php
	endif;
}