add[String]Attachment: allow to provide custom cid

+ fix cid use in base addStringAttachment

src/PHPMailerEnhanced/PHPMailerEnhanced.php

@@ -19,6 +19,18 @@ class PHPMailerEnhanced extends PHPMailer {
         $this->CharSet = PHPMailer::CHARSET_UTF8;
     }
 
+    /**
+     * Generate a new cid, ensuring it don't already exist in the mail
+     *
+     * @return string The new cid
+     */
+    public function cidGenerate (): string {
+        do {
+            $cid = uniqid('', true);
+        } while ($this->cidExists($cid));
+        return $cid;
+    }
+
     /**
      * @inheritDoc
      */
@@ -56,6 +68,61 @@ class PHPMailerEnhanced extends PHPMailer {
         return true;
     }
 
+    /**
+     * Add an attachment from a path on the filesystem.
+     * Never use a user-supplied path to a file!
+     * Returns false if the file could not be found or read.
+     * Explicitly *does not* support passing URLs; PHPMailer is not an HTTP client.
+     * If you need to do that, fetch the resource yourself and pass it in via a local file or string.
+     *
+     * @param string $path        Path to the attachment
+     * @param string $name        Overrides the attachment name
+     * @param string $encoding    File encoding (see $Encoding)
+     * @param string $type        MIME type, e.g. `image/jpeg`; determined automatically from $path if not specified
+     * @param string $disposition Disposition to use
+     * @param string|null $cid    The attachment cid ; Null to use name (if provided) or filename. Use {@see static::cidGenerate()} to get a random cid
+     *
+     * @return bool True on successfully adding an attachment
+     *
+     * @throws Exception If an error occurs
+     */
+    public function addAttachment ($path, $name = '', $encoding = self::ENCODING_BASE64, $type = '', $disposition = 'attachment', ?string $cid = null): bool {
+        if (!parent::addAttachment($path, $name, $encoding, $type, $disposition)) {
+            return false;
+        }
+        if ($cid !== null) {
+            $lastAttachment = &$this->attachment[array_key_last($this->attachment)];
+            $lastAttachment[7] = $cid;
+        }
+        return true;
+    }
+    /**
+     * Add a string or binary attachment (non-filesystem). This method can be used to attach ascii or binary data, such as a BLOB record from a database.
+     *
+     * @param string $string      String attachment data
+     * @param string $filename    Name of the attachment
+     * @param string $encoding    File encoding (see $Encoding)
+     * @param string $type        File extension (MIME) type
+     * @param string $disposition Disposition to use
+     * @param string|null $cid    The attachment cid ; Null to randomly generate one (see {@see static::cidGenerate()})
+     *
+     * @return bool True on successfully adding an attachment
+     *
+     * @throws Exception If an error occurs
+     */
+    public function addStringAttachment ($string, $filename, $encoding = self::ENCODING_BASE64, $type = '', $disposition = 'attachment', ?string $cid = null): bool {
+        if (!parent::addStringAttachment($string, $filename, $encoding, $type, $disposition)) {
+            return false;
+        }
+
+        // Not sur why, but addStringAttachment force “0” as cid instead of generating one → force a random cid if not provided
+        $cid ??= $this->cidGenerate();
+        $lastAttachment = &$this->attachment[array_key_last($this->attachment)];
+        $lastAttachment[7] = $cid;
+
+        return true;
+    }
+
     /**
      * Process local files to embed then in mail
      *
@@ -96,18 +163,12 @@ class PHPMailerEnhanced extends PHPMailer {
             return;
         }
         //endregion
-        //region Generate an unique “cid“ prefix
-        $cidNumber = 1;
-        do {
-            $cidPrefix = uniqid() . '_';
-        } while ($this->cidExists($cidPrefix . $cidNumber));
-        $embeddedImages = [];
-        //endregion
 
         //region Search all link (“src” or “href“ attribute)
+        $embeddedImages = [];
         $body = preg_replace_callback(
             '#(?<=src="|href=")[^"]+(?=")#i',
-            function (array $match) use ($localDirectory, $cidPrefix, &$cidNumber, &$embeddedImages): string {
+            function (array $match) use ($localDirectory, &$embeddedImages): string {
                 $link = $match[0];
 
                 //region Check the link has no protocol (http, cid, etc.) or it's “file”
@@ -133,8 +194,8 @@ class PHPMailerEnhanced extends PHPMailer {
                 }
                 //endregion
 
-                //region Associate a “cid“ to the file
-                $cid = $cidPrefix . ($cidNumber++);
+                //region Associate a cid to the file
+                $cid = $this->cidGenerate();
                 $embeddedImages[$cid] = $path;
                 //endregion