A sequence of characters.

A series of case-insensitive characters. Internally, upper-case ASCII characters will be converted to lower-case.

A series of characters that may contain newlines. Text tends to indicate human-oriented text, as opposed to a machine format.

A series of case-insensitive characters that may contain newlines.

An integer. You are alternatively permitted to pass a string of digits instead, which will be cast to an integer using (int).

A floating point number. You are alternatively permitted to pass a numeric string (as defined by is_numeric()), which will be cast to a float using (float).

A boolean. You are alternatively permitted to pass an integer 0 or 1 (other integers are not permitted) or a string "on", "true" or "1" for true, and "off", "false" or "0" for false.

An array whose values are true, e.g. array('key' => true, 'key2' => true). You are alternatively permitted to pass an array list of the keys array('key', 'key2') or a comma-separated string of keys "key, key2". If you pass an array list of values, ensure that your values are strictly numerically indexed: array('key1', 2 => 'key2') will not do what you expect and emits a warning.

An array which has consecutive integer indexes, e.g. array('val1', 'val2'). You are alternatively permitted to pass a comma-separated string of keys "val1, val2". If your array is not in this form, array_values is run on the array and a warning is emitted.

An array which is a mapping of keys to values, e.g. array('key1' => 'val1', 'key2' => 'val2'). You are alternatively permitted to pass a comma-separated string of key-colon-value strings, e.g. "key1: val1, key2: val2".

An arbitrary PHP value of any type.