How can you determine the length of a string in pixels in PHP?

To determine the length of a string in pixels in PHP, you can use the `imagettfbbox()` function from the GD library. This function calculates the bounding box of a text using a specified TrueType font. By subtracting the starting x-coordinate from the ending x-coordinate, you can get the width of the text in pixels.

$text = "Hello, World!";
$font = 4; // Font size
$fontFile = "arial.ttf"; // Path to TrueType font file
$bbox = imagettfbbox($font, 0, $fontFile, $text);
$width = $bbox[2] - $bbox[0]; // Calculate width in pixels
echo "The width of the text is: " . $width . " pixels";