How to use filter_var function in php? (code example)

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First introduce PHP Filter

PHP manual address: http://php.net/manual/zh/ref.filter.php

PHP filters are used to validate and filter data from non-secure sources (such as user input).

Installation

The filter function is an integral part of the core of PHP. No installation is required to use these functions.

PHP Filter Function

PHP: Indicates the earliest PHP version that supports this function.

Function	Description	PHP
filter_has_var( )	Check whether a variable of the specified input type exists.	5
filter_id()	Returns the ID number of the specified filter.	5
filter_input()	Get input from outside the script and filter it.	5
filter_input_array()	Get multiple inputs from outside the script and filter them.	5
filter_list()	Returns an array containing all supported filters.	5
filter_var_array()	Get multiple variables and filter them.	5
filter_var()	Get a variable and filter it.	5

PHP Filters

## FILTER_SANITIZE_URLRemove all characters except letters, numbers and $-_. !*'(),{}|//^~[]`a8093152e673feb7aba1828c43532094#%";/?:@&= FILTER_SANITIZE_NUMBER_INTRemove all characters except numbers and -##FILTER_SANITIZE_NUMBER_FLOATFILTER_SANITIZE_MAGIC_QUOTESFILTER_UNSAFE_RAWFILTER_VALIDATE_INTFILTER_VALIDATE_BOOLEANFILTER_VALIDATE_FLOATFILTER_VALIDATE_REGEXPFILTER_VALIDATE_URLFILTER_VALIDATE_EMAILFILTER_VALIDATE_IP

ID Name	Description
FILTER_CALLBACK	Call user-defined function to filter data.
FILTER_SANITIZE_STRING	Remove tags, remove or encode special characters.
FILTER_SANITIZE_STRIPPED	"string" Alias ​​for the filter.
FILTER_SANITIZE_ENCODED	URL-encode string, remove or encode special characters.
FILTER_SANITIZE_SPECIAL_CHARS	HTML escape character '"a8093152e673feb7aba1828c43532094& and characters with ASCII value less than 32.
FILTER_SANITIZE_EMAIL	Remove all characters except letters, numbers and !#$%&'* -/=?^_`{|}~@.[]
Remove all characters, In addition to numbers, - and.,eE.
Apply addslashes().
Does not do any filtering, remove or encode special characters.
Validates values ​​as integers in the specified range.
If it is "1", "true", "on" and "yes", it returns true, if it is "0", "false" , "off", "no" and "", returns false. Otherwise NULL is returned.
Validate the value as a floating point number.
Validates values ​​based on regexp, a Perl-compatible regular expression.
Validate the value as a URL.
Validate the value as an e-mail.
Validate the value as an IP address

filter_var —

Use a specific filter to filter a variable

Definition and usage

filter_var() function filters through the specified filter variable.

If successful, return filtered data, if failed, return false.

Syntax

filter_var(variable, filter, options)

Parametersvariable filteroptions

Description
Required. Specifies the variables to filter.
Optional. Specifies the ID of the filter to use.
Specifies an array containing flags/options. Check the possible flags and options for each filter.

For example:

if(filter_var($url, FILTER_VALIDATE_URL)){
 return true;
}

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