Adds symfony 5 support (#3)

* Adds symfony 5 support
* Fix lint errors

Author: kimpepper

composer.json

@@ -9,10 +9,10 @@
     }
   ],
   "require": {
-    "php": "^7.1",
+    "php": "^7.2",
     "ext-json": "*",
-    "symfony/property-access": "^3.4||^4.4",
-    "symfony/serializer": "^3.4||^4.4"
+    "symfony/property-access": "^3.4||^4.4||^5.0",
+    "symfony/serializer": "^3.4||^4.4||^5.0"
   },
   "require-dev": {
     "drupal/coder": "^8.3.8",

src/Counter.php

@@ -2,8 +2,6 @@
 
 namespace PNX\Prometheus;
 
-use InvalidArgumentException;
-
 /**
  * Value object representing a Prometheus counter type.
  */
@@ -31,7 +29,7 @@ public function getType(): string {
    */
   public function set($value, array $labels = []) {
     if (!$this->isValidValue($value)) {
-      throw new InvalidArgumentException("A count value must be a positive integer.");
+      throw new \InvalidArgumentException("A count value must be a positive integer.");
     }
     $key = $this->getKey($labels);
     $this->labelledValues[$key] = new LabelledValue($this->getName(), $value, $labels);

src/Metric.php

@@ -2,8 +2,6 @@
 
 namespace PNX\Prometheus;
 
-use InvalidArgumentException;
-
 /**
  * Value object to represent a prometheus metric.
  */
@@ -98,7 +96,7 @@ public function getLabelledValues() {
    */
   protected function validateName($name): void {
     if (!preg_match(self::METRIC_NAME_REGEX, $name)) {
-      throw new InvalidArgumentException("Invalid name: '" . $name . "'");
+      throw new \InvalidArgumentException("Invalid name: '" . $name . "'");
     }
   }