Created if-Statement (markdown)

if-Statement.md

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+Use `elseif` instead of `else if`. For sake of consistency `else if` is considered bad practice.
+
+<details><summary>Example</summary><div><br>
+
+**Bad**
+
+```PHP
+if($conditionA) {
+
+} else if($conditionB) {
+
+}
+```
+
+**Good**
+
+```PHP
+if($conditionA) {
+
+} elseif($conditionB) {
+
+}
+```
+
+</div></details><br>
+
+_Reference_: [`PSR2.ControlStructures.ElseIfDeclaration`](https://github.com/squizlabs/PHP_CodeSniffer/blob/master/src/Standards/PSR2/Sniffs/ControlStructures/ElseIfDeclarationSniff.php)
+
+***
+
+Empty statements are considered bad practice and must be avoided.
+
+<details><summary>Example</summary><div><br>
+
+**Bad**
+
+```PHP
+if($condition) {
+    // empty statement
+} else {
+    // do something here
+}
+```
+
+**Good** (invert condition)
+
+```PHP
+if(!$condition) {
+    // do something
+}
+```
+
+</div></details><br>
+
+_Reference_: [`Generic.CodeAnalysis.EmptyStatement`](https://github.com/squizlabs/PHP_CodeSniffer/blob/master/src/Standards/Generic/Sniffs/CodeAnalysis/EmptyStatementSniff.php)
+
+***
+
+Do not write unconditional if-statements. If-statements without conditions are considered bad practice and must be avoided.
+
+<details><summary>Example</summary><div><br>
+
+```PHP
+if(true) {
+
+}
+```
+
+</div></details><br>
+
+_Reference_: [`Generic.CodeAnalysis.UnconditionalIfStatement`](https://github.com/squizlabs/PHP_CodeSniffer/blob/master/src/Standards/Generic/Sniffs/CodeAnalysis/UnconditionalIfStatementSniff.php)