source: generatepress/1.2.9.7/inc/sanitize.php

<?php
/**
 * Sanitize integers
 * @since 1.0.8
 */
function generate_sanitize_integer( $input ) {
        return absint( $input );
}

/**
 * Sanitize checkbox values
 * @since 1.0.8
 */
function generate_sanitize_checkbox( $input ) {
        if ( $input ) {
                $output = '1';
        } else {
                $output = false;
        }
        return $output;
}

/**
 * Sanitize header layout
 * @since 1.0.8
 */
function generate_sanitize_header_layout( $input ) {
    $valid = array(
        'fluid-header' => __( 'Fluid / Full Width', 'generate' ),
                'contained-header' => __( 'Contained', 'generate' )
    );
 
    if ( array_key_exists( $input, $valid ) ) {
        return $input;
    } else {
        return 'fluid-header';
    }
}

/**
 * Sanitize navigation layout
 * @since 1.0.8
 */
function generate_sanitize_nav_layout( $input ) {
    $valid = array(
        'fluid-nav' => __( 'Fluid / Full Width', 'generate' ),
                'contained-nav' => __( 'Contained', 'generate' )
    );
 
    if ( array_key_exists( $input, $valid ) ) {
        return $input;
    } else {
        return 'fluid-nav';
    }
}

/**
 * Sanitize typography dropdown
 * @since 1.1.10
 */
function generate_sanitize_typography( $input ) 
{

        $google_fonts = ( get_transient('generate_font_list') ? get_transient('generate_font_list') : array() );
        
        $not_google = array(
                'inherit',
                'Arial, Helvetica, sans-serif',
                'Century Gothic',
                'Comic Sans MS',
                'Courier New',
                'Georgia, Times New Roman, Times, serif',
                'Helvetica',
                'Impact',
                'Lucida Console',
                'Lucida Sans Unicode',
                'Palatino Linotype',
                'Tahoma, Geneva, sans-serif',
                'Trebuchet MS, Helvetica, sans-serif',
                'Verdana, Geneva, sans-serif'
        );
        
        $valid = array_merge( $google_fonts, $not_google );
        
    if ( in_array( $input, $valid ) ) {
        return $input;
    } else {
        return 'Open Sans:300,300italic,regular,italic,600,600italic,700,700italic,800,800italic';
    }
}

/**
 * Sanitize font weight
 * @since 1.1.10
 */
function generate_sanitize_font_weight( $input ) {

    $valid = array(
        'normal',
                'bold',
                '100',
                '200',
                '300',
                '400',
                '500',
                '600',
                '700',
                '800',
                '900'
    );
 
    if ( in_array( $input, $valid ) ) {
        return $input;
    } else {
        return 'normal';
    }
}

/**
 * Sanitize text transform
 * @since 1.1.10
 */
function generate_sanitize_text_transform( $input ) {

    $valid = array(
        'none',
                'capitalize',
                'uppercase',
                'lowercase'
    );
 
    if ( in_array( $input, $valid ) ) {
        return $input;
    } else {
        return 'none';
    }
}

/**
 * Sanitize navigation alignment
 * @since 1.1.1
 */
function generate_sanitize_alignment( $input ) {
    $valid = array(
        'left' => __( 'Left', 'generate' ),
                'center' => __( 'Center', 'generate' ),
                'right' => __( 'Right', 'generate' )
    );
 
    if ( array_key_exists( $input, $valid ) ) {
        return $input;
    } else {
        return 'left';
    }
}

/**
 * Sanitize navigation alignment
 * @since 1.1.1
 */
function generate_sanitize_nav_search( $input ) {
    $valid = array(
        'enable' => __( 'Enabled', 'generate' ),
                'disable' => __( 'Disabled', 'generate' )
    );
 
    if ( array_key_exists( $input, $valid ) ) {
        return $input;
    } else {
        return 'disable';
    }
}

/**
 * Sanitize navigation position
 * @since 1.0.8
 */
function generate_sanitize_nav_position( $input ) {
    $valid = array(
        'nav-below-header' => __( 'Below Header', 'generate' ),
                'nav-above-header' => __( 'Above Header', 'generate' ),
                'nav-float-right' => __( 'Float Right', 'generate' ),
                'nav-left-sidebar' => __( 'Left Sidebar', 'generate' ),
                'nav-right-sidebar' => __( 'Right Sidebar', 'generate' ),
                '' => __( 'No Navigation', 'generate' )
    );
 
    if ( array_key_exists( $input, $valid ) ) {
        return $input;
    } else {
        return '';
    }
}

/**
 * Sanitize content layout
 * @since 1.0.8
 */
function generate_sanitize_content_layout( $input ) {
    $valid = array(
        'separate-containers' => __( 'Separate Containers', 'generate' ),
                'one-container' => __( 'One Container', 'generate' )
    );
 
    if ( array_key_exists( $input, $valid ) ) {
        return $input;
    } else {
        return 'separate-containers';
    }
}

/**
 * Sanitize sidebar layout
 * @since 1.0.8
 */
function generate_sanitize_sidebar_layout( $input ) {
    $valid = array(
        'left-sidebar' => __( 'Sidebar / Content', 'generate' ),
                'right-sidebar' => __( 'Content / Sidebar', 'generate' ),
                'no-sidebar' => __( 'Content (no sidebars)', 'generate' ),
                'both-sidebars' => __( 'Sidebar / Content / Sidebar', 'generate' ),
                'both-left' => __( 'Sidebar / Sidebar / Content', 'generate' ),
                'both-right' => __( 'Content / Sidebar / Sidebar', 'generate' )
    );
 
    if ( array_key_exists( $input, $valid ) ) {
        return $input;
    } else {
        return 'right-sidebar';
    }
}

/**
 * Sanitize footer layout
 * @since 1.0.8
 */
function generate_sanitize_footer_layout( $input ) {
    $valid = array(
        'fluid-footer' => __( 'Fluid / Full Width', 'generate' ),
                'contained-footer' => __( 'Contained', 'generate' )
    );
 
    if ( array_key_exists( $input, $valid ) ) {
        return $input;
    } else {
        return 'fluid-footer';
    }
}

/**
 * Sanitize footer widgets
 * @since 1.0.8
 */
function generate_sanitize_footer_widgets( $input ) {
    $valid = array(
        '0' => '0',
                '1' => '1',
                '2' => '2',
                '3' => '3',
                '4' => '4',
                '5' => '5'
    );
 
    if ( array_key_exists( $input, $valid ) ) {
        return $input;
    } else {
        return '3';
    }
}

/**
 * Sanitize blog excerpt
 * @since 1.0.8
 */
function generate_sanitize_blog_excerpt( $input ) {
    $valid = array(
        'full' => __( 'Show full post', 'generate' ),
                'excerpt' => __( 'Show excerpt', 'generate' )
    );
 
    if ( array_key_exists( $input, $valid ) ) {
        return $input;
    } else {
        return 'full';
    }
}

/**
 * Sanitize colors
 * Allow blank value
 * @since 1.2.9.6
 */
function generate_sanitize_hex_color( $color ) {
    if ( '' === $color )
        return '';
 
    // 3 or 6 hex digits, or the empty string.
    if ( preg_match('|^#([A-Fa-f0-9]{3}){1,2}$|', $color ) )
        return $color;
 
    return '';
}