feat(#46): get rid of (some) PHP deprecation warnings

- use issets, default local var values, better/newer language constructs

lib/Cake/Model/Behavior/ContainableBehavior.php

@@ -370,6 +370,7 @@ class ContainableBehavior extends ModelBehavior {
  */
 	public function fieldDependencies(Model $Model, $map, $fields = array()) {
 		if ($fields === false) {
+			$fields = [];
 			foreach ($map as $parent => $children) {
 				foreach ($children as $type => $bindings) {
 					foreach ($bindings as $dependency) {

lib/Cake/Model/Datasource/Database/Mysql.php

@@ -838,7 +838,7 @@ class Mysql extends DboSource {
  */
 	public function value($data, $column = null, $null = true) {
 		$value = parent::value($data, $column, $null);
-		if (is_numeric($value) && substr($column, 0, 3) === 'set') {
+		if (is_numeric($value) && $column !== null && str_starts_with($column, 'set')) {
 			return $this->_connection->quote($value);
 		}
 		return $value;

lib/Cake/Model/Datasource/DboSource.php

@@ -3270,15 +3270,16 @@ class DboSource extends DataSource {
 		}
 		$sign = isset($result[3]);
 
+		if ($length === null) {
+			// prevent deprecation warnings
+			return null;
+		}
+
 		$isFloat = in_array($type, array('dec', 'decimal', 'float', 'numeric', 'double'));
 		if ($isFloat && strpos($length, ',') !== false) {
 			return $length;
 		}
 
-		if ($length === null) {
-			return null;
-		}
-
 		if (isset($types[$type])) {
 			return (int)$length;
 		}

lib/Cake/Utility/CakeText.php

@@ -193,7 +193,7 @@ class CakeText {
 		$dataReplacements = array_combine($hashKeys, array_values($data));
 		foreach ($dataReplacements as $tmpHash => $tmpValue) {
 			$tmpValue = (is_array($tmpValue)) ? '' : $tmpValue;
-			$str = str_replace($tmpHash, $tmpValue, $str);
+			$str = str_replace($tmpHash, $tmpValue ?? '', $str);
 		}
 
 		if (!isset($options['format']) && isset($options['before'])) {

lib/Cake/Utility/Inflector.php

@@ -483,7 +483,7 @@ class Inflector {
  */
 	public static function underscore($camelCasedWord) {
 		if (!($result = static::_cache(__FUNCTION__, $camelCasedWord))) {
-			$underscoredWord = preg_replace('/(?<=\\w)([A-Z])/', '_\\1', $camelCasedWord);
+			$underscoredWord = preg_replace('/(?<=\\w)([A-Z])/', '_\\1', $camelCasedWord ?? '');
 			$result = mb_strtolower($underscoredWord);
 			static::_cache(__FUNCTION__, $camelCasedWord, $result);
 		}

lib/Cake/View/Helper.php

@@ -573,7 +573,7 @@ class Helper extends CakeObject {
 		if ($setScope === true) {
 			$this->_modelScope = $entity;
 		}
-		$parts = array_values(Hash::filter(explode('.', $entity)));
+		$parts = $entity !== null ? array_values(Hash::filter(explode('.', $entity))) : [];
 		if (empty($parts)) {
 			return;
 		}