diff --git a/.travis.yml b/.travis.yml
index f8e4e723e..c3e98dc44 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -31,8 +31,11 @@ matrix:
     - php: 7.3
       env: DB=SQLITE
 
-    - php: 7.4snapshot
+    - php: 7.4
       env: DB=SQLITE INSTALL_PHPUNIT_FORK=1
+      dist: xenial
+      services:
+        - mysql
 
     # CMS test
     - php: 5.5
diff --git a/admin/code/LeftAndMain.php b/admin/code/LeftAndMain.php
index fc2e940cd..574c6b67e 100644
--- a/admin/code/LeftAndMain.php
+++ b/admin/code/LeftAndMain.php
@@ -1993,7 +1993,7 @@ class LeftAndMain_TreeNode extends ViewableData {
 		// Get additional filter classes
 		if($this->filter && ($filterClasses = $this->filter->getPageClasses($this->obj))) {
 			if(is_array($filterClasses)) {
-				$filterClasses = implode(' ' . $filterClasses);
+				$filterClasses = implode(' ', $filterClasses);
 			}
 			$classes .= ' ' . $filterClasses;
 		}
diff --git a/email/Email.php b/email/Email.php
index 4e4585f83..4ce048d35 100644
--- a/email/Email.php
+++ b/email/Email.php
@@ -768,7 +768,7 @@ class Email extends ViewableData {
 				return strtr($email, $obfuscated);
 			case 'hex' :
 				$encoded = '';
-				for ($x=0; $x < strlen($email); $x++) $encoded .= '&#x' . bin2hex($email{$x}).';';
+				for ($x=0; $x < strlen($email); $x++) $encoded .= '&#x' . bin2hex($email[$x]).';';
 				return $encoded;
 			default:
 				user_error('Email::obfuscate(): Unknown obfuscation method', E_USER_NOTICE);
diff --git a/forms/Form.php b/forms/Form.php
index d2f7c00e7..be066abed 100644
--- a/forms/Form.php
+++ b/forms/Form.php
@@ -1810,7 +1810,7 @@ class Form extends RequestHandler {
 	 * @return string
 	 */
 	public function extraClass() {
-		return implode(array_unique($this->extraClasses), ' ');
+		return implode(' ', array_unique($this->extraClasses));
 	}
 
 	/**
diff --git a/i18n/i18n.php b/i18n/i18n.php
index c1912fc19..909d3d1df 100644
--- a/i18n/i18n.php
+++ b/i18n/i18n.php
@@ -2615,7 +2615,7 @@ class i18n extends SS_Object implements TemplateGlobalProvider, Flushable {
 				if(is_dir($themesBase)) {
 					foreach(scandir($themesBase) as $theme) {
 						if(
-							strpos($theme, Config::inst()->get('SSViewer', 'theme')) === 0
+							strpos($theme, (string)Config::inst()->get('SSViewer', 'theme')) === 0
 							&& file_exists("{$themesBase}/{$theme}/lang/")
 						) {
 							$filename = $adapter->getFilenameForLocale($locale);
diff --git a/model/Image.php b/model/Image.php
index abb5fe3d1..aafcd50fa 100644
--- a/model/Image.php
+++ b/model/Image.php
@@ -767,7 +767,7 @@ class Image extends File implements Flushable {
 		foreach($matches as $formatdir) {
 			$prepend[] = $formatdir[0];
 		}
-		$filename = implode($prepend) . $filename;
+		$filename = implode('', $prepend) . $filename;
 
 		if (!preg_match($pattern['FullPattern'], $filename)) {
 			throw new InvalidArgumentException('Filename ' . $filename
diff --git a/model/fieldtypes/Text.php b/model/fieldtypes/Text.php
index c0313d7f7..558994d4e 100644
--- a/model/fieldtypes/Text.php
+++ b/model/fieldtypes/Text.php
@@ -88,7 +88,7 @@ class Text extends StringField {
 			}
 		}
 
-		return count($output)==0 ? '' : implode($output, '. ') . '.';
+		return count($output)==0 ? '' : implode('. ', $output) . '.';
 	}