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Filters in Php
PHP filters are used to validating data means determine if the data is in proper form and sanitizing data means remove any illegal character from the data external input.
The PHP filter extension has many of the functions needed for checking user input, and is designed to make data validation easier and quicker.
Use of Filters
There are many web applications receive external input that is :
- User input from a form
- Cookies
- Web services data
- Server variables
- Database query results
Example:
<html>
<head>
<style>
table, th, td
{
border: 1px solid black;
border-collapse: collapse;
}
th, td
{
padding: 8px;
}
</style>
</head>
<body>
<table>
<tr>
<td>Filter Name</td>
<td>Filter ID</td>
</tr>
<?php
foreach (filter_list() as $id =>$filter)
{
echo '<tr><td>' . $filter . '</td><td>' . filter_id($filter) . '</td></tr>';
}
?>
</table>
</body>
</html>
Output:
Some Filter Functions are:
| Function Name | Description |
| filter_has_var() | Checks if a variable of a specified input type exist |
| filter_id() | Returns the filter ID of a specified filter name |
| filter_input() | Gets an external variable (e.g. from form input) and optionally filters it. |
| filter_input_array() | Gets external variables (e.g. from form input) and optionally filters them |
| filter_list() | Returns a list of all supported filters |
| filter_var_array() | Gets multiple variables and filter them |
| filter_var() | Filters a variable with a specified filter |
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