New generic string validation rule.

Author: lonnieezell

system/Validation/FormatRules.php

@@ -121,6 +121,23 @@ public function alpha_numeric_space(string $str = null): bool
 
 	//--------------------------------------------------------------------
 
+	/**
+	 * Any type of string
+	 *
+	 * Note: we specifically do NOT type hint $str here so that
+	 * it doesn't convert numbers into strings.
+	 *
+	 * @param string|null $str
+	 *
+	 * @return boolean
+	 */
+	public function string($str = null): bool
+	{
+		return is_string($str);
+	}
+
+	//--------------------------------------------------------------------
+
 	/**
 	 * Decimal number
 	 *

tests/system/Validation/FormatRulesTest.php

@@ -325,6 +325,47 @@ public function ipProvider()
 
 	//--------------------------------------------------------------------
 
+	/**
+	 * @dataProvider stringProvider
+	 *
+	 * @param $str
+	 * @param $expected
+	 */
+	public function testString($str, $expected)
+	{
+		$data = [
+			'foo' => $str,
+		];
+
+		$this->validation->setRules([
+			'foo' => 'string',
+		]);
+
+		$this->assertEquals($expected, $this->validation->run($data));
+	}
+
+	//--------------------------------------------------------------------
+
+	public function stringProvider()
+	{
+		return [
+			[
+				'123',
+				true,
+			],
+			[
+				123,
+				false,
+			],
+			[
+				'hello',
+				true,
+			],
+		];
+	}
+
+	//--------------------------------------------------------------------
+
 	/**
 	 * @dataProvider alphaProvider
 	 *

user_guide_src/source/libraries/validation.rst

@@ -661,28 +661,29 @@ alpha_numeric           No          Fails if field contains anything other than
 alpha_numeric_space     No          Fails if field contains anything other than alpha-numeric characters, numbers or space.
 decimal                 No          Fails if field contains anything other than a decimal number.
 differs                 Yes         Fails if field does not differ from the one in the parameter.                                   differs[field_name]
-exact_length            Yes         Fails if field is not exactly the parameter value. One or more comma-separated values.                                             exact_length[5] or exact_length[5,8,12]
+exact_length            Yes         Fails if field is not exactly the parameter value. One or more comma-separated values.          exact_length[5] or exact_length[5,8,12]
 greater_than            Yes         Fails if field is less than or equal to the parameter value or not numeric.                     greater_than[8]
 greater_than_equal_to   Yes         Fails if field is less than the parameter value, or not numeric.                                greater_than_equal_to[5]
+if_exist                No          If this rule is present, validation will only return possible errors if the field key exists,
+                                    regardless of its value.
 in_list                 Yes         Fails if field is not within a predetermined list.                                              in_list[red,blue,green]
 integer                 No          Fails if field contains anything other than an integer.
 is_natural              No          Fails if field contains anything other than a natural number: 0, 1, 2, 3, etc.
 is_natural_no_zero      No          Fails if field contains anything other than a natural number, except zero: 1, 2, 3, etc.
+is_unique               Yes         Checks if this field value exists in the database. Optionally set a                             is_unique[table.field,ignore_field,ignore_value]
+                                    column and value to ignore, useful when updating records to ignore itself.
 less_than               Yes         Fails if field is greater than or equal to the parameter value or not numeric.                  less_than[8]
 less_then_equal_to      Yes         Fails if field is greater than the parameter value or not numeric.                              less_than_equal_to[8]
 matches                 Yes         The value must match the value of the field in the parameter.                                   matches[field]
 max_length              Yes         Fails if field is longer than the parameter value.                                              max_length[8]
 min_length              Yes         Fails if field is shorter than the parameter value.                                             min_length[3]
 numeric                 No          Fails if field contains anything other than numeric characters.
 regex_match             Yes         Fails if field does not match the regular expression.                                           regex_match[/regex/]
-if_exist                No          If this rule is present, validation will only return possible errors if the field key exists,
-                                    regardless of its value.
 permit_empty            No          Allows the field to receive an empty array, empty string, null or false.
 required                No          Fails if the field is an empty array, empty string, null or false.
 required_with           Yes         The field is required when any of the other required fields are present in the data.            required_with[field1,field2]
 required_without        Yes         The field is required when all of the other fields are present in the data but not required.    required_without[field1,field2]
-is_unique               Yes         Checks if this field value exists in the database. Optionally set a                             is_unique[table.field,ignore_field,ignore_value]
-                                    column and value to ignore, useful when updating records to ignore itself.
+string                  No          A generic alternative to the alpha* rules that confirms the element is a string
 timezone                No          Fails if field does match a timezone per ``timezone_identifiers_list``
 valid_base64            No          Fails if field contains anything other than valid Base64 characters.
 valid_json              No          Fails if field does not contain a valid JSON string.