Introduction
This extension filters data by either validating or sanitizing it. This is especially useful when the data source contains unknown (or foreign) data, like user supplied input. For example, this data may come from an HTML form.
There are two main types of filtering: validation and sanitization.
Validation is used to validate or check if the data meets certain qualifications. For example, passing in FILTER_VALIDATE_EMAIL will determine if the data is a valid email address, but will not change the data itself.
Sanitization will sanitize the data, so it may alter it by removing undesired characters. For example, passing in FILTER_SANITIZE_EMAIL will remove characters that are inappropriate for an email address to contain. That said, it does not validate the data.
Flags are optionally used with both validation and sanitization to tweak behaviour according to need. For example, passing in FILTER_FLAG_SCHEME_REQUIRED while filtering an URL will require a scheme (like http://) to be present.
Installation
The filter extension is enabled by default as of PHP 5.2.0. Before this time an experimental PECL extension was used, however, the PECL version is no longer recommended or updated.
courtesy php.net
for more info check this
PHP: Validate filters - Manual
This extension filters data by either validating or sanitizing it. This is especially useful when the data source contains unknown (or foreign) data, like user supplied input. For example, this data may come from an HTML form.
There are two main types of filtering: validation and sanitization.
Validation is used to validate or check if the data meets certain qualifications. For example, passing in FILTER_VALIDATE_EMAIL will determine if the data is a valid email address, but will not change the data itself.
Sanitization will sanitize the data, so it may alter it by removing undesired characters. For example, passing in FILTER_SANITIZE_EMAIL will remove characters that are inappropriate for an email address to contain. That said, it does not validate the data.
Flags are optionally used with both validation and sanitization to tweak behaviour according to need. For example, passing in FILTER_FLAG_SCHEME_REQUIRED while filtering an URL will require a scheme (like http://) to be present.
Installation
The filter extension is enabled by default as of PHP 5.2.0. Before this time an experimental PECL extension was used, however, the PECL version is no longer recommended or updated.
courtesy php.net
for more info check this
PHP: Validate filters - Manual