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Validating A Value Is An Integer

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When filtering a value that should be an integer filter_var() will return the filtered data, in this case the integer, or false if the value is not an integer. Floats are not integers: 

var_dump(filter_var('10', FILTER_VALIDATE_INT));
var_dump(filter_var('a10', FILTER_VALIDATE_INT));
var_dump(filter_var('10a', FILTER_VALIDATE_INT));
var_dump(filter_var(' ', FILTER_VALIDATE_INT));
var_dump(filter_var('10.00', FILTER_VALIDATE_INT));
var_dump(filter_var('10,000', FILTER_VALIDATE_INT));
var_dump(filter_var('-5', FILTER_VALIDATE_INT));
var_dump(filter_var('+7', FILTER_VALIDATE_INT));

Results: 

int(10)
bool(false)
bool(false)
bool(false)
bool(false)
bool(false)
int(-5)
int(7)

If you are expecting only digits, you can use a regular expression: 

if(is_string($_GET['entry']) && preg_match('#^[0-9]+$#', $_GET['entry']))
    // this is a digit (positive) integer
else
    // entry is incorrect

If you convert this value into an integer, you don’t have to do this check and so you can use filter_var.

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Filters, filter functions:
* Filters Filter Functions
* Validate Email Address
* Validating A Value Is An Integer
* Validating An Integer Falls In A Range
* Validate a URL
* Sanitize filters
* Validating Boolean Values
* Validating A Number Is A Float
* Validate A MAC Address
* Sanitze Email Addresses
* Sanitize Integers
* Sanitize URLs
* Sanitize Floats
* Validate IP Addresses
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