diff --git a/src/Cron/DayOfMonthField.php b/src/Cron/DayOfMonthField.php
index 60fa465..39ff597 100644
--- a/src/Cron/DayOfMonthField.php
+++ b/src/Cron/DayOfMonthField.php
@@ -94,9 +94,9 @@ public function isSatisfiedBy(DateTimeInterface $date, $value, bool $invert): bo
         }
 
         // Check to see if this is the nearest weekday to a particular value
-        if (strpos($value, 'W')) {
+        if ($wPosition = strpos($value, 'W')) {
             // Parse the target day
-            $targetDay = (int) substr($value, 0, strpos($value, 'W'));
+            $targetDay = (int) substr($value, 0, $wPosition);
             // Find out if the current day is the nearest day of the week
             $nearest = self::getNearestWeekday(
                 (int) $date->format('Y'),
diff --git a/src/Cron/DayOfWeekField.php b/src/Cron/DayOfWeekField.php
index 5ac003d..b9bbf48 100644
--- a/src/Cron/DayOfWeekField.php
+++ b/src/Cron/DayOfWeekField.php
@@ -68,8 +68,8 @@ public function isSatisfiedBy(DateTimeInterface $date, $value, bool $invert): bo
         $lastDayOfMonth = (int) $date->format('t');
 
         // Find out if this is the last specific weekday of the month
-        if (strpos($value, 'L')) {
-            $weekday = $this->convertLiterals(substr($value, 0, strpos($value, 'L')));
+        if ($lPosition = strpos($value, 'L')) {
+            $weekday = $this->convertLiterals(substr($value, 0, $lPosition));
             $weekday %= 7;
 
             $daysInMonth = (int) $date->format('t');
diff --git a/src/Cron/HoursField.php b/src/Cron/HoursField.php
index a7f8f33..413d138 100644
--- a/src/Cron/HoursField.php
+++ b/src/Cron/HoursField.php
@@ -25,7 +25,7 @@ class HoursField extends AbstractField
     /**
      * @var array|null Transitions returned by DateTimeZone::getTransitions()
      */
-    protected $transitions = null;
+    protected $transitions = [];
 
     /**
      * @var int|null Timestamp of the start of the transitions range
@@ -92,7 +92,7 @@ public function getPastTransition(DateTimeInterface $date): ?array
                 $dtLimitStart->getTimestamp(),
                 $dtLimitEnd->getTimestamp()
             );
-            if ($this->transitions === false) {
+            if (empty($this->transitions)) {
                 return null;
             }
             $this->transitionsStart = $dtLimitStart->getTimestamp();