Useful Vanilla PHP and WordPress helper functions.

general.php

<?php
// This file contains general useful PHP functions that can be included everywhere.

/**
 * Wrapper for writing the interactions to /wp-content/uploads/ file
 *
 * @param $message
 * @param string $filename
 */
function dg_log_write( $message, $filename = "log.txt" ) {
	$log_file_path = dirname( __FILE__ ) . '/' . $filename; // Change path if needed
	if ( is_object( $message ) || is_array( $message ) ) {
		ob_start();
		var_dump( $message );
		$message = ob_get_clean();
	}
	$fp = fopen( $log_file_path, 'a+' );
	fwrite( $fp, $message . "\n" );
	fclose( $fp );
}

/**
 * Replaces german umlauts with normal characters in a given string.
 *
 * @param $str
 * @return string
 */
function dg_umlauts_fix( $str ) {
	$umlauts = array(
		'Ä' => 'Ae',
		'Ö' => 'Oe',
		'Ü' => 'Ue',
		'ü' => 'ue',
		'ö' => 'oe',
		'ä' => 'ae',
		'ß' => 'ss'
	);
	$str     = strtr( $str, $umlauts );

	return $str;
}

/**
 * Returns the client ip address
 * @return mixed
 */
function dg_get_client_ip() {
	if ( getenv( 'HTTP_CLIENT_IP' ) ) {
		$ip_address = getenv( 'HTTP_CLIENT_IP' );
	} else if ( getenv( 'HTTP_X_FORWARDED_FOR' ) ) {
		$ip_address = getenv( 'HTTP_X_FORWARDED_FOR' );
	} else if ( getenv( 'HTTP_X_FORWARDED' ) ) {
		$ip_address = getenv( 'HTTP_X_FORWARDED' );
	} else if ( getenv( 'HTTP_FORWARDED_FOR' ) ) {
		$ip_address = getenv( 'HTTP_FORWARDED_FOR' );
	} else if ( getenv( 'HTTP_FORWARDED' ) ) {
		$ip_address = getenv( 'HTTP_FORWARDED' );
	} else if ( getenv( 'REMOTE_ADDR' ) ) {
		$ip_address = getenv( 'REMOTE_ADDR' );
	} else {
		$ip_address = false;
	}

	return $ip_address;
}

/**
 * Returns true if string contains another string
 *
 * @param $text
 * @param $string
 *
 * @return bool
 */
function dg_str_contains( $text, $string ) {
	return ( strpos( $text, $string ) !== false );
}

/**
 * Pluck an array of values from an array. (Only for PHP 5.3+)
 *
 * @param  $array - data
 * @param  $key - value you want to pluck from array
 *
 * @return array plucked array only with key data
 */
function dg_array_pluck( $array, $key ) {
	return array_map( function ( $v ) use ( $key ) {
		return is_object( $v ) ? $v->$key : $v[ $key ];
	}, $array );
}

gravityforms.php

<?php
/**
 * Returns the value by Input name (value in Allow this field to be populated dynamically)
 * @param $fields
 * @param $input_name
 * @param $choice_id
 *
 * @return string
 */
function dg_gf_get_value_by_input_name($fields, $input_name, $choice_id = 0) {
	$value = NULL;
	//error_log(print_r($_POST, true));
	foreach($fields as $field) {
		if($field->inputName == $input_name) {
			if($choice_id > 0) {
				$handle = 'input_' . $field->id . '_' . $choice_id;
			} else {
				$handle = 'input_' . $field->id;
			}
			$value = isset($_POST[$handle]) ? $_POST[$handle] : NULL;
		}
	}
	return $value;
}

wordpress.php

<?php
// This file contains useful WordPress functions that can be included in any WP theme or plugin and used.

/**
 * Used to upload single image into WP, returns false or the attachment_id that is created in the db
 * Example input element: <input type=file name=file_handler/>
 * @param $file_handler
 * @param $post_id
 *
 * @return bool|int|WP_Error
 */
function dg_handle_media_upload( $file_handler, $post_id ) {
	if ( ! file_exists( $_FILES[ $file_handler ]['tmp_name'] ) || ! is_uploaded_file( $_FILES[ $file_handler ]['tmp_name'] ) ) {
		return false;
	}
	require_once( ABSPATH . 'wp-admin/includes/image.php' );
	require_once( ABSPATH . 'wp-admin/includes/file.php' );
	require_once( ABSPATH . 'wp-admin/includes/media.php' );
	$attachment_id = media_handle_upload( $file_handler, $post_id );
	if ( ! is_wp_error( $attachment_id ) ) {
		return $attachment_id;
	} else {
		return false;
	}
}
/**
 * Handles multiple files and stores into WP based on one input and returns the stored attachment ids.
 * Example input element: <input type=file name=file_handler[]/>
 * @param $file_handler
 * @param $post_id
 *
 * @return array
 */
function dg_handle_multiple_media_uploads( $file_handler, $post_id ) {
	$attachment_ids = array();
	if ( $_FILES ) {
		$files = isset( $_FILES[ $file_handler ] ) ? $_FILES[ $file_handler ] : array();
		if ( ! empty( $files ) ) {
			foreach ( $files['name'] as $key => $value ) {
				if ( $files['name'][ $key ] ) {
					$file   = array(
						'name'     => $files['name'][ $key ],
						'type'     => $files['type'][ $key ],
						'tmp_name' => $files['tmp_name'][ $key ],
						'error'    => $files['error'][ $key ],
						'size'     => $files['size'][ $key ]
					);
					$attachment_ids[] = dg_handle_media_upload( $file_handler, $post_id);
				}
			}
		}
	}
	return $attachment_ids;
}


/**
 * Returns latitude and longitude from Google's geocoder with transient cache
 * for WordPress
 *
 * Note: Set constant ___GOOGLE__YOUR__API__KEY___ with your google api key.
 *
 * @param string $address
 * @param bool $force_new_data
 *
 * @return array
 */
function dg_get_lat_long( $address, $force_new_data = false ) {
	if ( $force_new_data ) {
		delete_transient( $address );
	}
	$transient_key = sanitize_key($address);
	// Cache address to save Google geocoding calls.
	if ( false === ( $coordinates = get_transient( $transient_key ) ) ) {
		$address            = str_replace( " ", "+", $address );
		$json               = file_get_contents( "https://maps.googleapis.com/maps/api/geocode/json?address=" . $address . "&key=" . ___YOUR__API__KEY___ );
		$json               = json_decode( $json );
		$coordinates['lat'] = $json->{'results'}[0]->{'geometry'}->{'location'}->{'lat'};
		$coordinates['lng'] = $json->{'results'}[0]->{'geometry'}->{'location'}->{'lng'};
		if( $coordinates['lat'] !== NULL && $coordinates['lng'] !== NULL ) {
			set_transient( $transient_key, $coordinates, DAY_IN_SECONDS * 15 );
		}
	}
	return $coordinates;
}