Be careful about the default flags for the default filters.
They should be set explicitly.
For example, to configure the default filter to behave exactly like
htmlspecialchars() the default flags must be set to
0, as shown in the example below.
Example #1 Configuring the default filter to act like htmlspecialchars
Default flags to apply when the default filter is set.
This is set to FILTER_FLAG_NO_ENCODE_QUOTES
by default for backwards compatibility reasons.
See FILTER_FLAG_*
constants for available flags.