Updated String concatenation (markdown)

String-concatenation.md

@@ -38,3 +38,25 @@ $text = $greeting
 </div></details><br>
 
 _Reference_: [`Squiz.Strings.ConcatenationSpacing`](https://github.com/squizlabs/PHP_CodeSniffer/blob/master/src/Standards/Squiz/Sniffs/Strings/ConcatenationSpacingSniff.php)
+
+***
+
+While concatenation is useful for combining variables with other variables or static text. It should not be used to combine two sets of static text. See also: [Maximum line length](Maximum-line-length)
+
+<details><summary>Example</summary><div><br>
+
+**Bad**
+
+```PHP
+$text = 'This is' . 'a bad idea!';
+```
+
+**Good**
+
+```PHP
+$text = 'This is a good idea!';
+```
+
+</div></details><br>
+
+_Reference_: [`Generic.Strings.UnnecessaryStringConcat`](https://github.com/squizlabs/PHP_CodeSniffer/blob/master/src/Standards/Generic/Sniffs/Strings/UnnecessaryStringConcatSniff.php)