FILTER_VALIDATE_FLOAT constant in PHP

The FILTER_VALIDATE_FLOAT constant validates whether a value is a valid float number. It returns the filtered data on success, or FALSE on failure.

Syntax

filter_var($value, FILTER_VALIDATE_FLOAT, $flags)

Parameters

$value − The value to validate as a float

$flags (optional) − Additional flags like FILTER_FLAG_ALLOW_THOUSAND

Return Value

Returns the validated float value on success, or FALSE on failure.

Example 1: Basic Float Validation

<?php
    $var = 291.9;
    $result = filter_var($var, FILTER_VALIDATE_FLOAT);
    var_dump($result);
?>

float(291.9)

Example 2: Testing Different Values

<?php
    $values = ['123.45', '0.5', 'abc', '1,234.56', ''];
    
    foreach ($values as $value) {
        $result = filter_var($value, FILTER_VALIDATE_FLOAT);
        echo "Value: '$value' - Result: ";
        var_dump($result);
        echo "<br>";
    }
?>

Value: '123.45' - Result: float(123.45)
Value: '0.5' - Result: float(0.5)
Value: 'abc' - Result: bool(false)
Value: '1,234.56' - Result: bool(false)
Value: '' - Result: bool(false)

Example 3: Using Flags

<?php
    $value = '1,234.56';
    
    // Without flag - fails
    $result1 = filter_var($value, FILTER_VALIDATE_FLOAT);
    echo "Without flag: ";
    var_dump($result1);
    
    // With FILTER_FLAG_ALLOW_THOUSAND - succeeds
    $result2 = filter_var($value, FILTER_VALIDATE_FLOAT, FILTER_FLAG_ALLOW_THOUSAND);
    echo "With thousand separator flag: ";
    var_dump($result2);
?>

Without flag: bool(false)
With thousand separator flag: float(1234.56)

Conclusion

FILTER_VALIDATE_FLOAT is essential for validating numeric input. Use FILTER_FLAG_ALLOW_THOUSAND when working with formatted numbers containing comma separators.