Decamelize function (#6615)

* New decamelize helper.

* Add additional tests

system/Helpers/inflector_helper.php

@@ -185,6 +185,21 @@ if (! function_exists('underscore')) {
     }
 }
 
+if (! function_exists('decamelize')) {
+    /**
+     * Decamelize
+     *
+     * Takes multiple words separated by camel case and
+     * underscores them.
+     *
+     * @param string $string Input string
+     */
+    function decamelize(string $string): string
+    {
+        return strtolower(preg_replace(['/([a-z\d])([A-Z])/', '/([^_])([A-Z][a-z])/'], '$1_$2', trim($string)));
+    }
+}
+
 if (! function_exists('humanize')) {
     /**
      * Humanize

tests/system/Helpers/InflectorHelperTest.php

@@ -285,4 +285,41 @@ final class InflectorHelperTest extends CIUnitTestCase
             $this->assertSame($suffixed, $ordinalized);
         }
     }
+
+    public function testDecamelizeToSnakeCase()
+    {
+        $strings = [
+            'simpleTest'      => 'simple_test',
+            'easy'            => 'easy',
+            'HTML'            => 'html',
+            'simpleXML'       => 'simple_xml',
+            'PDFLoad'         => 'pdf_load',
+            'startMIDDLELast' => 'start_middle_last',
+            'AString'         => 'a_string',
+            'Some4Numbers234' => 'some4_numbers234',
+            'TEST123String'   => 'test123_string',
+            'hello_world'     => 'hello_world',
+            'hello___world'   => 'hello___world',
+            '_hello_world_'   => '_hello_world_',
+            'HelloWorld'      => 'hello_world',
+            'helloWorldFoo'   => 'hello_world_foo',
+            'hello_World'     => 'hello_world',
+            'hello-world'     => 'hello-world',
+            'myHTMLFiLe'      => 'my_html_fi_le',
+            'aBaBaB'          => 'a_ba_ba_b',
+            'BaBaBa'          => 'ba_ba_ba',
+            'libC'            => 'lib_c',
+            'a'               => 'a',
+            'A'               => 'a',
+            'aB'              => 'a_b',
+            'AB'              => 'ab',
+            'ab'              => 'ab',
+            'Ab'              => 'ab',
+        ];
+
+        foreach ($strings as $camelized => $expects) {
+            $underscored = decamelize($camelized);
+            $this->assertSame($expects, $underscored);
+        }
+    }
 }

user_guide_src/source/changelogs/v4.3.0.rst

@@ -148,6 +148,7 @@ Helpers and Functions
 - Added new Form helper function :php:func:`validation_errors()`, :php:func:`validation_list_errors()` and :php:func:`validation_show_error()` to display Validation Errors.
 - You can set the locale to :php:func:`route_to()` if you pass a locale value as the last parameter.
 - Added :php:func:`request()` and :php:func:`response()` functions.
+- Add :php:func:`decamelize()` function to convert camelCase to snake_case.
 
 Others
 ======

user_guide_src/source/helpers/inflector_helper.rst

@@ -85,6 +85,17 @@ The following functions are available:
 
     .. literalinclude:: inflector_helper/007.php
 
+.. php:function:: decamelize($string)
+
+    :param    string    $string: Input string
+    :returns:    String containing underscores between words
+    :rtype:    string
+
+    Takes multiple words in camelCase or PascalCase and converts them to snake_case.
+    Example:
+
+    .. literalinclude:: inflector_helper/007.php
+
 .. php:function:: humanize($string[, $separator = '_'])
 
     :param    string    $string: Input string

user_guide_src/source/helpers/inflector_helper/014.php

@@ -0,0 +1,3 @@
+<?php
+
+echo decamelize('myDogSpot'); // Prints 'my_dog_spot'