Source

File: wp-includes/post.php

function sanitize_post_field( $field, $value, $post_id, $context = 'display' ) {
	$int_fields = array( 'ID', 'post_parent', 'menu_order' );
	if ( in_array( $field, $int_fields, true ) ) {
		$value = (int) $value;
	}

	// Fields which contain arrays of integers.
	$array_int_fields = array( 'ancestors' );
	if ( in_array( $field, $array_int_fields, true ) ) {
		$value = array_map( 'absint', $value );
		return $value;
	}

	if ( 'raw' === $context ) {
		return $value;
	}

	$prefixed = false;
	if ( false !== strpos( $field, 'post_' ) ) {
		$prefixed        = true;
		$field_no_prefix = str_replace( 'post_', '', $field );
	}

	if ( 'edit' === $context ) {
		$format_to_edit = array( 'post_content', 'post_excerpt', 'post_title', 'post_password' );

		if ( $prefixed ) {

			/**
			 * Filters the value of a specific post field to edit.
			 *
			 * The dynamic portion of the hook name, `$field`, refers to the post
			 * field name.
			 *
			 * @since 2.3.0
			 *
			 * @param mixed $value   Value of the post field.
			 * @param int   $post_id Post ID.
			 */
			$value = apply_filters( "edit_{$field}", $value, $post_id );

			/**
			 * Filters the value of a specific post field to edit.
			 *
			 * The dynamic portion of the hook name, `$field_no_prefix`, refers to
			 * the post field name.
			 *
			 * @since 2.3.0
			 *
			 * @param mixed $value   Value of the post field.
			 * @param int   $post_id Post ID.
			 */
			$value = apply_filters( "{$field_no_prefix}_edit_pre", $value, $post_id );
		} else {
			$value = apply_filters( "edit_post_{$field}", $value, $post_id );
		}

		if ( in_array( $field, $format_to_edit, true ) ) {
			if ( 'post_content' === $field ) {
				$value = format_to_edit( $value, user_can_richedit() );
			} else {
				$value = format_to_edit( $value );
			}
		} else {
			$value = esc_attr( $value );
		}
	} elseif ( 'db' === $context ) {
		if ( $prefixed ) {

			/**
			 * Filters the value of a specific post field before saving.
			 *
			 * The dynamic portion of the hook name, `$field`, refers to the post
			 * field name.
			 *
			 * @since 2.3.0
			 *
			 * @param mixed $value Value of the post field.
			 */
			$value = apply_filters( "pre_{$field}", $value );

			/**
			 * Filters the value of a specific field before saving.
			 *
			 * The dynamic portion of the hook name, `$field_no_prefix`, refers
			 * to the post field name.
			 *
			 * @since 2.3.0
			 *
			 * @param mixed $value Value of the post field.
			 */
			$value = apply_filters( "{$field_no_prefix}_save_pre", $value );
		} else {
			$value = apply_filters( "pre_post_{$field}", $value );

			/**
			 * Filters the value of a specific post field before saving.
			 *
			 * The dynamic portion of the hook name, `$field`, refers to the post
			 * field name.
			 *
			 * @since 2.3.0
			 *
			 * @param mixed $value Value of the post field.
			 */
			$value = apply_filters( "{$field}_pre", $value );
		}
	} else {

		// Use display filters by default.
		if ( $prefixed ) {

			/**
			 * Filters the value of a specific post field for display.
			 *
			 * The dynamic portion of the hook name, `$field`, refers to the post
			 * field name.
			 *
			 * @since 2.3.0
			 *
			 * @param mixed  $value   Value of the prefixed post field.
			 * @param int    $post_id Post ID.
			 * @param string $context Context for how to sanitize the field. Possible
			 *                        values include 'edit', 'display',
			 *                        'attribute' and 'js'.
			 */
			$value = apply_filters( "{$field}", $value, $post_id, $context );
		} else {
			$value = apply_filters( "post_{$field}", $value, $post_id, $context );
		}

		if ( 'attribute' === $context ) {
			$value = esc_attr( $value );
		} elseif ( 'js' === $context ) {
			$value = esc_js( $value );
		}
	}

	return $value;
}