N°7068 - Add emulation for apc_exists function (#460)

* Emulate missing apc_exists

* Apply suggestions from code review

Co-authored-by: Molkobain <lajarige.guillaume@free.fr>

* Update core/apc-emulation.php

---------

Co-authored-by: Molkobain <lajarige.guillaume@free.fr>

core/apc-emulation.php

@@ -97,6 +97,28 @@ function apc_delete($key)
 	return $bRet1 || $bRet2;
 }
 
+/**
+ * Checks if APCu emulation key exists
+ * @param string|string[] $keys A string, or an array of strings, that contain keys.
+ * @return bool|string[] Returns TRUE if the key exists, otherwise FALSE
+ * Or if an array was passed to keys, then an array is returned that
+ * contains all existing keys, or an empty array if none exist.
+ */
+function apc_exists($keys)
+{
+	if (is_array($keys)) {
+		$aExistingKeys = [];
+		foreach ($keys as $sKey) {
+			if (apcFile::ExistsOneFile($sKey)) {
+				$aExistingKeys[] = $sKey;
+			}
+		}
+		return $aExistingKeys;
+	} else {
+		return apcFile::ExistsOneFile($keys);
+	}
+}
+
 class apcFile
 {
 	// Check only once per request
@@ -183,6 +205,15 @@ class apcFile
 		return true;
 	}
 
+	/**
+	 * Check if cache key exists
+	 * @param $sKey
+	 * @return bool
+	 */
+	static public function ExistsOneFile($sKey) {
+		return is_file(self::GetCacheFileName('-' . $sKey)) || is_file(self::GetCacheFileName($sKey));
+	}
+
 	/** Get one cache entry content.
 	 * @param $sKey
 	 * @return bool|mixed