PHP Manual: ob_get

function ob_get_length(): int|false

This will return the length of the contents in the output buffer, in bytes.

This function has no parameters.

Returns the length of the output buffer contents, in bytes, or false if no buffering is active.

Example #1 A simple ob_get_length() example

<?php

ob_start();

echo "Hello ";

$len1 = ob_get_length();

echo "World";

$len2 = ob_get_length();

ob_end_clean();

echo $len1 . ", " . $len2;
?>

The above example will output:

6, 11

ob_get_length