PHP Floating Point Data Type

In PHP, the float data type represents any number with a decimal point or fractional part. Float values can be written in standard decimal notation or scientific notation using e or E. The size and precision of floats depend on the platform, though precision up to 14 decimal digits is commonly supported.

Syntax

// Standard decimal notation
$var = 5327.496;

// Scientific notation (lowercase e)
$var1 = 5.327496e3;

// Scientific notation (uppercase E) 
$var2 = 5.327496E3;

// Using underscore separator for readability (PHP 7.4+)
$var3 = 5_327.496;

For better readability, float literals may use "_" as a separation symbol, which is ignored by the PHP parser during processing. This feature is available since PHP 7.4.

Standard Decimal Notation

The most common way to represent float values is using standard decimal notation ?

<?php
$price = 99.95;
$temperature = -12.5;
$ratio = 0.75;

echo "Price: " . $price . "<br>";
echo "Temperature: " . $temperature . "<br>"; 
echo "Ratio: " . $ratio . "<br>";
?>

Price: 99.95
Temperature: -12.5
Ratio: 0.75

Scientific Notation

Scientific notation is useful for very large or very small numbers ?

<?php
$large_num = 5.327496e3;    // 5327.496
$small_num = 2.5e-4;        // 0.00025
$uppercase = 1.23E6;        // 1230000

echo "Large: " . $large_num . "<br>";
echo "Small: " . $small_num . "<br>";
echo "Uppercase: " . $uppercase . "<br>";
?>

Large: 5327.496
Small: 0.00025
Uppercase: 1230000

Underscore Separator

Note: Underscore separator in numeric literals requires PHP 7.4 or higher.

PHP 7.4 introduced underscore separators for improved readability of large numbers ?

<?php
$readable = 1_234_567.89;
$scientific = 1.234_567e6;

echo "Readable: " . $readable . "<br>";
echo "Scientific: " . $scientific . "<br>";
?>

Readable: 1234567.89
Scientific: 1234567

Type Checking

You can verify if a variable contains a float value using the is_float() function ?

<?php
$float_val = 3.14;
$int_val = 42;

var_dump(is_float($float_val));  // bool(true)
var_dump(is_float($int_val));    // bool(false)
?>

bool(true)
bool(false)

Conclusion

PHP floats support standard decimal notation, scientific notation, and underscore separators for readability. Use scientific notation for very large or small numbers, and remember that underscore separators are only available in PHP 7.4 and later versions.